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• Database Owner Conundrum

  - by Johnm

  Have you ever restored a database from a production environment on Server A into a development environment on Server B and had some items, such as Service Broker, mysteriously cease functioning? You might want to consider reviewing the database owner property of the database. The Scenario Recently, I was developing some messaging functionality that utilized the Service Broker feature of SQL Server in a development environment. Within the instance of the development environment resided two databases: One was a restored version of a production database that we will call "RestoreDB". The second database was a brand new database that has yet to exist in the production environment that we will call "DevDB". The goal is to setup a communication path between RestoreDB and DevDB that will later be implemented into the production database. After implementing all of the Service Broker objects that are required to communicate within a database as well as between two databases on the same instance I found myself a bit confounded. My testing was showing that the communication was successful when it was occurring internally within DevDB; but the communication between RestoreDB and DevDB did not appear to be working. Profiler to the rescue After carefully reviewing my code for any misspellings, missing commas or any other minor items that might be a syntactical cause of failure, I decided to launch Profiler to aid in the troubleshooting. After simulating the cross database messaging, I noticed the following error appearing in Profiler: An exception occurred while enqueueing a message in the target queue. Error: 33009, State: 2. The database owner SID recorded in the master database differs from the database owner SID recorded in database '[Database Name Here]'. You should correct this situation by resetting the owner of database '[Database Name Here]' using the ALTER AUTHORIZATION statement. Now, this error message is a helpful one. Not only does it identify the issue in plain language, it also provides a potential solution. An execution of the following query that utilizes the catalog view sys.transmission_queue revealed the same error message for each communication attempt: SELECT     * FROM        sys.transmission_queue; Seeing the situation as a learning opportunity I dove a bit deeper. Reviewing the database properties  The owner of a specific database can be easily viewed by right-clicking the database in SQL Server Management Studio and selecting the "properties" option. The owner is listed on the "General" page of the properties screen. In my scenario, the database in the production server was created by Frank the DBA; therefore his server login appeared as the owner: "ServerName\Frank". While this is interesting information, it certainly doesn't tell me much in regard to the SID (security identifier) and its existence, or lack thereof, in the master database as the error suggested. I pulled together the following query to gather more interesting information: SELECT     a.name     , a.owner_sid     , b.sid     , b.name     , b.type_desc FROM        master.sys.databases a     LEFT OUTER JOIN master.sys.server_principals b         ON a.owner_sid = b.sid WHERE     a.name not in ('master','tempdb','model','msdb'); This query also helped identify how many other user databases in the instance were experiencing the same issue. In this scenario, I saw that there were no matching SIDs in server_principals to the owner SID for my database. What login should be used as the database owner instead of Frank's? The system stored procedure sp_helplogins will provide a list of the valid logins that can be used. Here is an example of its use, revealing all available logins: EXEC sp_helplogins;  Fixing a hole The error message stated that the recommended solution was to execute the ALTER AUTHORIZATION statement. The full statement for this scenario would appear as follows: ALTER AUTHORIZATION ON DATABASE:: [Database Name Here] TO [Login Name]; Another option is to execute the following statement using the sp_changedbowner system stored procedure; but please keep in mind that this stored procedure has been deprecated and will likely disappear in future versions of SQL Server: EXEC dbo.sp_changedbowner @loginname = [Login Name]; .And They Lived Happily Ever After Upon changing the database owner to an existing login and simulating the inner and cross database messaging the errors have ceased. More importantly, all messages sent through this feature now successfully complete their journey. I have added the ownership change to my restoration script for the development environment.

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• Use your own domain email and tired of SPAM? SPAMfighter FTW

  - by Dave Campbell

  I wouldn't post this if I hadn't tried it... and I paid for it myself, so don't anybody be thinking I'm reviewing something someone sent me! Long ago and far away I got very tired of local ISPs and 2nd phone lines and took the plunge and got hooked up to cable... yeah I know the 2nd phone line concept may be hard for everyone to understand, but that's how it was in 'the old days'. To avoid having to change email addresses all the time, I decided to buy a domain name, get minimal hosting, and use that for all email into the house. That way if I changed providers, all the email addresses wouldn't have to change. Of course, about a dozen domains later, I have LOTS of pop email addresses and even an exchange address to my client's server... times have changed. What also has changed is the fact that we get SPAM... 'back in the day' when I was a beta tester for the first ISP in Phoenix, someone tried sending an ad to all of us, and what he got in return for his trouble was a bunch of core dumps that locked up his email... if you don't know what a core dump is, ask your grandfather. But in today's world, we're all much more civilized than that, and as with many things, the criminals seem to have much more rights than we do, so we get inundated with email offering all sorts of wild schemes that you'd have to be brain-dead to accept, but yet... if people weren't accepting them, they'd stop sending them. I keep hoping that survival of the smartest would weed out the mental midgets that respond and then the jumk email stop, but that hasn't happened yet anymore than finding high-quality hearing aids at the checkout line of Safeway because of all the dimwits playing music too loud inside their car... but that's another whole topic and I digress. So what's the solution for all the spam? And I mean *all*... on that old personal email address, I am now getting over 150 spam messages a day! Yes I know that's why God invented the delete key, but I took it on as a challenge, and it's a matter of principle... why should I switch email addresses, or convert from [email protected] to something else, or have all my email filtered through some service just because some A-Hole somewhere has a site up trying to phish Ma & Pa Kettle (ask your grandfather about that too) out of their retirement money? Well... I got an email from my cousin the other day while I was writing yet another email rule, and there was a banner on the bottom of his email that said he was protected by SPAMfighter. SPAMfighter huh.... so I took a look at their site, and found yet one more of the supposed tools to help us. But... I read that they're a Microsoft Gold Partner... and that doesn't come lightly... so I took a gamble and here's what I found: I installed it, and had to do a couple things: 1) SPAMfighter stuffed the SPAMfighter folder into my client's exchange address... I deleted it, made a new SPAMfighter folder where I wanted it to go, then in the SPAMfighter Clients settings for Outlook, I told it to put all spam there. 2) It didn't seem to be doing anything. There's a ribbon button that you can select "Block", and I did that, wondering if I was 'training' it, but it wasn't picking up duplicates 3) I sent email to support, and wrote a post on the forum (not to self: reply to that post). By the time the folks from the home office responded, it was the next day, and first up, SPAMfighter knocked down everything that came through when Outlook opend... two thumbs up! I disabled my 'garbage collection' rule from Outlook, and told Outlook not to use the junk folder thinking it was interfering. 4) Day 2 seemed to go about like Day 1... but I hung in there. 5) Day 3 is now a whole new day... I had left Outlook open and hadn't looked at the PC since sometime late yesterday afternoon, and when I looked this morning, *every bit* of spam was in the SPAMfighter folder!! I'm a new paying customer After watching SPAMfighter work this morning, I've purchased a 1-year license, and I now can sit and watch as emails come in and disappear from my inbox into the SPAMfighter folder. No more continual tweaking of the rules. I've got SPAMfighter set to 'Very Hard' filtering... personally I'd rather pull the few real emails out of the SPAMfighter folder than pull spam out of the real folders. Yes this is simply another way of using the delete key, but you know what? ... it feels good :) Here's a screenshot of the stats after just about 48 hours of being onboard: Note that all the ones blocked by me were during Day 1 and 2... I've blocked none today, and everything is blocked. Stay in the 'Light!

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• Hiring New IT Employees versus Promoting Internally for IT Positions

  Recently I was asked my opinion regarding the hiring of IT professionals in regards to the option of hiring new IT employees versus promoting internally for IT positions. After thinking a little more about this question regarding staffing, specifically pertaining to promoting internally verses new employees; I think my answer to this question is that it truly depends on the situation. However, in most cases I would side with promoting internally. The key factors in this decision should be based on a company/department’s current values, culture, attitude, and existing priorities.  For example if a company values retaining all of its hard earned business knowledge then they would tend to promote existing employees internal over hiring a new employee. Moreover, the company will have to pay to train an existing employee to learn a new technology and the learning curve for some technologies can be very steep. Conversely, if a company values new technologies and technical proficiency over business knowledge then a company would tend to hire new employees because they may already have experience with a technology that the company is planning on using. In this scenario, the company would have to take on the additional overhead of allowing a new employee to learn how the business operates prior to them being fully effective. To illustrate my points above let us look at contractor that builds in ground pools for example.  He has the option to hire employees that are very strong but use small shovels to dig, or employees weak in physical strength but use large shovels to dig. Which employee should the contractor use to dig a hole for a new in ground pool? If we compare the possible candidates for this job we will find that they are very similar to hiring someone internally verses a new hire. The first example represents the existing workers that are very strong regarding the understanding how the business operates and the reasons why in a specific manner. However this employee could be potentially weaker than an outsider pertaining to specific technologies and would need some time to build their technical prowess for a new position much like the strong worker upgrading their shovels in order to remove more dirt at once when digging. The other employee is very similar to hiring a new person that may already have the large shovel but will need to increase their strength in order to use the shovel properly and efficiently so that they can move a maximum amount of dirt in a minimal amount of time. This can be compared to new employ learning how a business operates before they can be fully functional and integrated in the company/department. Another key factor in this dilemma pertains to existing employee and their passion for their work, their ability to accept new responsibility when given, and the willingness to take on responsibilities when they see a need in the business. As much as possible should be considered in this decision down to the mood of the team, the quality of existing staff, learning cure for both technology and business, and the potential side effects of the existing staff.  In addition, there are many more consideration based on the current team/department/companies culture and mood. There are several factors that need to be considered when promoting an individual or hiring new blood for a team. They both can provide great benefits as well as create controversy to a group. Personally, staffing especially in the IT world is like building a large scale system in that all of the components and modules must fit together and preform as one cohesive system in the same way a team must come together using their individually acquired skills so that they can work as one team.  If a module is out of place or is nonexistent then the rest of the team will suffer until the all of its issues are addressed and resolved. Benefits of Promoting Internally Internal promotions give employees a reason to constantly upgrade their technology, business, and communication skills if they want to further their career Employees can control their own destiny based on personal desires Employee already knows how the business operates Companies can save money by promoting internally because the initial overhead of allowing new hires to learn how a company operates is very expensive Newly promoted employees can assist in training their replacements while transitioning to their new role within a company. Existing employees already have a proven track record in regards fitting in with the business culture; this is always an unknown with all new hires Benefits of a New Hire New employees can energize and excite existing employees New employees can bring new ideas and advancements in technology New employees can offer a different perspective on existing issues based on their past experience. As you can see the decision to promote an existing employee from within a company verses hiring a new person should be based on several factors that should ultimately place the business in the best possible situation for the immediate and long term future. How would you handle this situation? Would you hire a new employee or promote from within?

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• Performance triage

  - by Dave

  Folks often ask me how to approach a suspected performance issue. My personal strategy is informed by the fact that I work on concurrency issues. (When you have a hammer everything looks like a nail, but I'll try to keep this general). A good starting point is to ask yourself if the observed performance matches your expectations. Expectations might be derived from known system performance limits, prototypes, and other software or environments that are comparable to your particular system-under-test. Some simple comparisons and microbenchmarks can be useful at this stage. It's also useful to write some very simple programs to validate some of the reported or expected system limits. Can that disk controller really tolerate and sustain 500 reads per second? To reduce the number of confounding factors it's better to try to answer that question with a very simple targeted program. And finally, nothing beats having familiarity with the technologies that underlying your particular layer. On the topic of confounding factors, as our technology stacks become deeper and less transparent, we often find our own technology working against us in some unexpected way to choke performance rather than simply running into some fundamental system limit. A good example is the warm-up time needed by just-in-time compilers in Java Virtual Machines. I won't delve too far into that particular hole except to say that it's rare to find good benchmarks and methodology for java code. Another example is power management on x86. Power management is great, but it can take a while for the CPUs to throttle up from low(er) frequencies to full throttle. And while I love "turbo" mode, it makes benchmarking applications with multiple threads a chore as you have to remember to turn it off and then back on otherwise short single-threaded runs may look abnormally fast compared to runs with higher thread counts. In general for performance characterization I disable turbo mode and fix the power governor at "performance" state. Another source of complexity is the scheduler, which I've discussed in prior blog entries. Lets say I have a running application and I want to better understand its behavior and performance. We'll presume it's warmed up, is under load, and is an execution mode representative of what we think the norm would be. It should be in steady-state, if a steady-state mode even exists. On Solaris the very first thing I'll do is take a set of "pstack" samples. Pstack briefly stops the process and walks each of the stacks, reporting symbolic information (if available) for each frame. For Java, pstack has been augmented to understand java frames, and even report inlining. A few pstack samples can provide powerful insight into what's actually going on inside the program. You'll be able to see calling patterns, which threads are blocked on what system calls or synchronization constructs, memory allocation, etc. If your code is CPU-bound then you'll get a good sense where the cycles are being spent. (I should caution that normal C/C++ inlining can diffuse an otherwise "hot" method into other methods. This is a rare instance where pstack sampling might not immediately point to the key problem). At this point you'll need to reconcile what you're seeing with pstack and your mental model of what you think the program should be doing. They're often rather different. And generally if there's a key performance issue, you'll spot it with a moderate number of samples. I'll also use OS-level observability tools to lock for the existence of bottlenecks where threads contend for locks; other situations where threads are blocked; and the distribution of threads over the system. On Solaris some good tools are mpstat and too a lesser degree, vmstat. Try running "mpstat -a 5" in one window while the application program runs concurrently. One key measure is the voluntary context switch rate "vctx" or "csw" which reflects threads descheduling themselves. It's also good to look at the user; system; and idle CPU percentages. This can give a broad but useful understanding if your threads are mostly parked or mostly running. For instance if your program makes heavy use of malloc/free, then it might be the case you're contending on the central malloc lock in the default allocator. In that case you'd see malloc calling lock in the stack traces, observe a high csw/vctx rate as threads block for the malloc lock, and your "usr" time would be less than expected. Solaris dtrace is a wonderful and invaluable performance tool as well, but in a sense you have to frame and articulate a meaningful and specific question to get a useful answer, so I tend not to use it for first-order screening of problems. It's also most effective for OS and software-level performance issues as opposed to HW-level issues. For that reason I recommend mpstat & pstack as my the 1st step in performance triage. If some other OS-level issue is evident then it's good to switch to dtrace to drill more deeply into the problem. Only after I've ruled out OS-level issues do I switch to using hardware performance counters to look for architectural impediments.

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• Rebuilding CoasterBuzz, Part II: Hot data objects

  - by Jeff

  This is the second post, originally from my personal blog, in a series about rebuilding one of my Web sites, which has been around for 12 years. More: Part I: Evolution, and death to WCF After the rush to get moving on stuff, I temporarily lost interest. I went almost two weeks without touching the project, in part because the next thing on my backlog was doing up a bunch of administrative pages. So boring. Unfortunately, because most of the site's content is user-generated, you need some facilities for editing data. CoasterBuzz has a database full of amusement parks and roller coasters. The entities enjoy the relationships that you would expect, though they're further defined by "instances" of a coaster, to define one that has moved between parks as one, with different names and operational dates. And of course, there are pictures and news items, too. It's not horribly complex, except when you have to account for a name change and display just the newest name. In all previous versions, data access was straight SQL. As so much of the old code was rooted in 2003, with some changes in 2008, there wasn't much in the way of ORM frameworks going on then. Let me rephrase that, I mostly wasn't interested in ORM's. Since that time, I used a little LINQ to SQL in some projects, and a whole bunch of nHibernate while at Microsoft. Through all of that experience, I have to admit that these frameworks are often a bigger pain in the ass than not. They're great for basic crud operations, but when you start having all kinds of exotic relationships, they get difficult, and generate all kinds of weird SQL under the covers. The black box can quickly turn into a black hole. Sometimes you end up having to build all kinds of new expertise to do things "right" with a framework. Still, despite my reservations, I used the newer version of Entity Framework, with the "code first" modeling, in a science project and I really liked it. Since it's just a right-click away with NuGet, I figured I'd give it a shot here. My initial effort was spent defining the context class, which requires a bit of work because I deviate quite a bit from the conventions that EF uses, starting with table names. Then throw some partial querying of certain tables (where you'll find image data), and you're splitting tables across several objects (navigation properties). I won't go into the details, because these are all things that are well documented around the Internet, but there was a minor learning curve there. The basics of reading data using EF are fantastic. For example, a roller coaster object has a park associated with it, as well as a number of instances (if it was ever relocated), and there also might be a big banner image for it. This is stupid easy to use because it takes one line of code in your repository class, and by the time you pass it to the view, you have a rich object graph that has everything you need to display stuff. Likewise, editing simple data is also, well, simple. For this goodness, thank the ASP.NET MVC framework. The UpdateModel() method on the controllers is very elegant. Remember the old days of assigning all kinds of properties to objects in your Webforms code-behind? What a time consuming mess that used to be. Even if you're not using an ORM tool, having hydrated objects come off the wire is such a time saver. Not everything is easy, though. When you have to persist a complex graph of objects, particularly if they were composed in the user interface with all kinds of AJAX elements and list boxes, it's not just a simple matter of submitting the form. There were a few instances where I ended up going back to "old-fashioned" SQL just in the interest of time. It's not that I couldn't do what I needed with EF, it's just that the efficiency, both my own and that of the generated SQL, wasn't good. Since EF context objects expose a database connection object, you can use that to do the old school ADO.NET stuff you've done for a decade. Using various extension methods from POP Forums' data project, it was a breeze. You just have to stick to your decision, in this case. When you start messing with SQL directly, you can't go back in the same code to messing with entities because EF doesn't know what you're changing. Not really a big deal. There are a number of take-aways from using EF. The first is that you write a lot less code, which has always been a desired outcome of ORM's. The other lesson, and I particularly learned this the hard way working on the MSDN forums back in the day, is that trying to retrofit an ORM framework into an existing schema isn't fun at all. The CoasterBuzz database isn't bad, but there are design decisions I'd make differently if I were starting from scratch. Now that I have some of this stuff done, I feel like I can start to move on to the more interesting things on the backlog. There's a lot to do, but at least it's fun stuff, and not more forms that will be used infrequently.

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• Data Binding to Attached Properties

  - by Chris Gardner

  Originally posted on: http://geekswithblogs.net/freestylecoding/archive/2013/06/14/data-binding-to-attached-properties.aspx When I was working on my C#/XAML game framework, I discovered I wanted to try to data bind my sprites to background objects. That way, I could update my objects and the draw functionality would take care of the work for me. After a little experimenting and web searching, it appeared this concept was an impossible dream. Of course, when has that ever stopped me? In my typical way, I started to massively dive down the rabbit hole. I created a sprite on a canvas, and I bound it to a background object. <Canvas Name="GameField" Background="Black"> <Image Name="PlayerStrite" Source="Assets/Ship.png" Width="50" Height="50" Canvas.Left="{Binding X}" Canvas.Top="{Binding Y}"/> </Canvas> Now, we wire the UI item to the background item. public MainPage() { this.InitializeComponent(); this.Loaded += StartGame; }   void StartGame( object sender, RoutedEventArgs e ) { BindingPlayer _Player = new BindingPlayer(); _Player.X = Window.Current.Bounds.Height - PlayerSprite.Height; _Player.X = ( Window.Current.Bounds.Width - PlayerSprite.Width ) / 2.0; } Of course, now we need to actually have our background object. public class BindingPlayer : INotifyPropertyChanged { private double m_X; public double X { get { return m_X; } set { m_X = value; NotifyPropertyChanged(); } }   private double m_Y; public double Y { get { return m_Y; } set { m_Y = value; NotifyPropertyChanged(); } }   public event PropertyChangedEventHandler PropertyChanged; protected void NotifyPropertyChanged( [CallerMemberName] string p_PropertyName = null ) { if( PropertyChanged != null ) PropertyChanged( this, new PropertyChangedEventArgs( p_PropertyName ) ); } } I fired this baby up, and my sprite was correctly positioned on the screen. Maybe the sky wasn't falling after all. Wouldn't it be great if that was the case? I created some code to allow me to move the sprite, but nothing happened. This seems odd. So, I start debugging the application and stepping through code. Everything appears to be working. Time to dig a little deeper. After much profanity was spewed, I stumbled upon a breakthrough. The code only looked like it was working. What was really happening is that there was an exception being thrown in the background thread that I never saw. Apparently, the key call was the one to PropertyChanged. If PropertyChanged is not called on the UI thread, the UI thread ignores the call. Actually, it throws an exception and the background thread silently crashes. Of course, you'll never see this unless you're looking REALLY carefully. This seemed to be a simple problem. I just need to marshal this to the UI thread. Unfortunately, this object has no knowledge of this mythical UI Thread in which we speak. So, I had to pull the UI Thread out of thin air. Let's change our PropertyChanged call to look this. public event PropertyChangedEventHandler PropertyChanged; protected void NotifyPropertyChanged( [CallerMemberName] string p_PropertyName = null ) { if( PropertyChanged != null ) Windows.ApplicationModel.Core.CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync( Windows.UI.Core.CoreDispatcherPriority.Normal, new Windows.UI.Core.DispatchedHandler( () => { PropertyChanged( this, new PropertyChangedEventArgs( p_PropertyName ) ); } ) ); } Now, we raised our notification on the UI thread. Everything is fine, people are happy, and the world moves on. You may have noticed that I didn't await my call to the dispatcher. This was intentional. If I am trying to update a slew of sprites, I don't want thread being hung while I wait my turn. Thus, I send the message and move on. It is worth nothing that this is NOT the most efficient way to do this for game programming. We'll get to that in another blog post. However, it is perfectly acceptable for a business app that is running a background task that would like to notify the UI thread of progress on a periodic basis. It is worth noting that this code was written for a Windows Store App. You can do the same thing with WP8 and WPF. The call to the marshaler changes, but it is the same idea.

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• Is One Tool or a Suite of Tools Better for Scrum?

  - by Rob Wells

  G'day, Edit: We've been using Scrum very successfully for several years on several projects of varying sizes. In fact, our team developed the successful iPlayer project for the BBC using a classical Scrum approach. After using various combinations of tools, some high-tech, some low-tech, across these projects we now wish to try adopting a suitable tool suite. Our manager is to some extent attempting to force the adoption of a single suite of tools for Scrum. I've looked at the SO question "Best Scrum tools" and most people seem to recommend either: a suite of low-tech solutions, e.g. whiteboards, post-its, index cards, etc., or a monolithic tool that tries to satisfy as much as possible of the process, e.g. Agilo, Mingle, ScrumWorks, Target Process, etc. Our team is currently evaluating several different Scrum tools. However, we are looking at selecting a single, monolithic tool, e.g. Agilo. All of the "one-stop" solutions have their strengths and weaknesses with the serious enterprise type solutions being the best sort of fit. But all have some short comings. After reading the paper "Peer Code Review: An Agile Process" over at SmartBear I started wondering if we were trying to force adoption of a tool on a "best fit" basis. I think you can take a couple of reference artefacts of the Scrum development process, say user stories, epics and themes, and the code base which must use a well-known SCM, e.g. SVN, Hg, etc. Then if we take that as the common reference points for the tools employed then we would be able to use a group of tools to handle the different aspects of the Scrum process rather than try forcing a fit of a single tool would is a bit like forcing a square peg into the round hole. In this way, providing you've agreed your common reference points, you can use several tools, each performing their role better than a could be done by a single component in a monolithic tool suite. Is this a more sensible approach? Are the two reference points I mentioned above suitable, or is their a better choice of points where the tools would meet? cheers,

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• Potential issues using member's "from" address and the "sender" header

  - by Paul Burney

  Hi all, A major component of our application sends email to members on behalf of other members. Currently we set the "From" address to our system address and use a "Reply-to" header with the member's address. The issue is that replies from some email clients (and auto-replies/bounces) don't respect the "Reply-to" header so get sent to our system address, effectively sending them to a black hole. We're considering setting the "From" address to our member's address, and the "Sender" address to our system address. It appears this way would pass SPF and Sender-ID checks. Are there any reasons not to switch to this method? Are there any other potential issues? Thanks in advance, -Paul Here are way more details than you probably need: When the application was first developed, we just changed the "from" address to be that of the sending member as that was the common practice at the time (this was many years ago). We later changed that to have the "from" address be the member's name and our address, i.e., From: "Mary Smith" <[email protected]> With a "reply-to" header set to the member's address: Reply-To: "Mary Smith" <[email protected]> This helped with messages being mis-categorized as spam. As SPF became more popular, we added an additional header that would work in conjunction with our SPF records: Sender: <[email protected]> Things work OK, but it turns out that, in practice, some email clients and most MTA's don't respect the "Reply-To" header. Because of this, many members send messages to [email protected] instead of the desired member. So, I started envisioning various schemes to add data about the sender to the email headers or encode it in the "from" email address so that we could process the response and redirect appropriately. For example, From: "Mary Smith" <[email protected]> where the string after "messages" is a hash representing Mary Smith's member in our system. Of course, that path could lead to a lot of pain as we need to develop MTA functionality for our system address. I was looking again at the SPF documentation and found this page interesting: http://www.openspf.org/Best_Practices/Webgenerated They show two examples, that of evite.com and that of egreetings.com. Basically, evite.com is doing it the way we're doing it. The egreetings.com example uses the member's from address with an added "Sender" header. So the question is, are there any potential issues with using the egreetings method of the member's from address with a sender header? That would eliminate the replies that bad clients send to the system address. I don't believe that it solves the bounce/vacation/whitelist issue since those often send to the MAIL FROM even if Return Path is specified.

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• Stata - Multiple rotated plots on graph (including distributions on sides of axes)

  - by meerak

  I would like to produce a single graph containing both: (1) a scatter plot (2) either histograms or kernel density functions of the Y and X variables to the left of the Y axis and below the X axis. I found a graph that does this in MATLAB -- I would just like to produce something similar in Stata: That graph was produced using the following MATLAB code: n = 1000; rho = .7; Z = mvnrnd([0 0], [1 rho; rho 1], n); U = normcdf(Z); X = [gaminv(U(:,1),2,1) tinv(U(:,2),5)]; [n1,ctr1] = hist(X(:,1),20); [n2,ctr2] = hist(X(:,2),20); subplot(2,2,2); plot(X(:,1),X(:,2),'.'); axis([0 12 -8 8]); h1 = gca; title('1000 Simulated Dependent t and Gamma Values'); xlabel('X1 ~ Gamma(2,1)'); ylabel('X2 ~ t(5)'); subplot(2,2,4); bar(ctr1,-n1,1); axis([0 12 -max(n1)*1.1 0]); axis('off'); h2 = gca; subplot(2,2,1); barh(ctr2,-n2,1); axis([-max(n2)*1.1 0 -8 8]); axis('off'); h3 = gca; set(h1,'Position',[0.35 0.35 0.55 0.55]); set(h2,'Position',[.35 .1 .55 .15]); set(h3,'Position',[.1 .35 .15 .55]); colormap([.8 .8 1]); UPDATE: The Stata13 manual entry for "graph combine" has precisely this example (http://www.stata.com/manuals13/g-2graphcombine.pdf). Here is the code: use http://www.stata-press.com/data/r13/lifeexp, clear generate loggnp = log10(gnppc) label var loggnp "Log base 10 of GNP per capita" scatter lexp loggnp, ysca(alt) xsca(alt) xlabel(, grid gmax) fysize(25) saving(yx) twoway histogram lexp, fraction xsca(alt reverse) horiz fxsize(25) saving(hy) twoway histogram loggnp, fraction ysca(alt reverse) ylabel(,nogrid) xlabel(,grid gmax) saving(hx) graph combine hy.gph yx.gph hx.gph, hole(3) imargin(0 0 0 0) graphregion(margin(l=22 r=22)) title("Life expectancy at birth vs. GNP per capita") note("Source: 1998 data from The World Bank Group")

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• Referencing both an old version and new version of the same DLL (VB.Net)

  - by ckittel

  Consider the following situation: WidgetCompany produced a .NET DLL in 2006 called Widget.dll, version 1.0. I consumed this Widget.dll file throughout my VB.Net application. Over time, WidgetCompany has been updating Widget.dll, I never bothered to keep up, continuing to ship version 1.0 of Widget.dll with my software. It's now 2010, my project is now a VB.Net 3.5 application and WidgetCompany has come out with Widget.dll version 3.0. It looks and functions almost identical to Widget.dll version 1.0, using all the same namespaces and type names from before. However, Widget.dll version 3.0 has many run-time breaking changes since 1.0 and I cannot simply cut over to the new version; however, I don't want to continue developing against the 1.0 version and therefore keep digging myself deeper in the hole. What I want to do is do all new development in my project with Widget.dll version 3.0, whilst keeping Widget.dll version 1.0 around until I find time to convert all of my 1.0 consumption to the newer 3.0 code. Now, for starters, I obviously cannot simply reference both Widget.dll (Ver 1.0) and Widget.dll (Ver 3.0) in Visual Studio. Doing so gives me the following message: "A reference to 'Widget.dll' could not be added. A reference to the component 'Widget' already exists in the project." To work around that, I can simply rename version 3.0 Widget.dll to Widget.3.dll. But this is where I'm stuck. Any attempts to reference types found in "the dll" leads to ambiguity and the compiler obviously doesn't have any clue as to what I really want in this or that case. Is there something I can do that gives a DLL a new "root" Namespace or something? For example, if I could say "Widget.dll has a new root namespace of Legacy" then I could update existing code to reference the types found in Legacy.<RootNamespace> namespace while all new code could simply reference types from the <RootNamespace> namespace. Pipe dream or reality? Are there other solutions to situations this (besides "don't get in this situation in the first place")?

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• LINQ to XML, a problem conceptualizing how the tree should look.

  - by snark

  Have you ever had one of those days when you've dug a hole but your so deep in now that the only option is to keep on digging and see where you come out? I thought just for giggles in the latest component I'm writing to use LINQ to XML because it was about time I saw what all the hooplah was about. The problem: I am making a graph component that contains series of data that get graphed and then you can apply a formula to that series and graph another series then apply a formula to that series and so on. So I figured that I would do so in 2 steps, create (and manage) an XML representaion of the series and how they relate to each other, then pass this xml to a draw engine which draws. Conceptually its a tree, with the exception of the root all child series being based upon a parent (1 parent can have many children. So I should always be adding child nodes to their parent and if I delete a node(series) then I can simply delete the series and its descendants (then draw) and voila all the messy iterating through each node finding parents and children is unneccessary. Trouble is I dont know how to represent this tree in XML i.e. the structure. My first attempt saw me programatically adding each series as siblings, which worked like a treat because I ended up with an ordered list and thus my order of rendering was maintained. I had this <Chart> <Series id="1">seriesText1</Series> <Series id="2">seriesText2</Series> <Series id="3">seriesText3</Series> <Series id="4">seriesText4</Series> </Chart> I'm in a muddle now ... how can I represent a series and a series that has children series. If some-one can give me a hint to how my tree should look (perhaps with a snippet on how to programatically add nodes to their parents) All the examples I have read usually have some container elements such as <ContactS> or <BookS> but my head says I have <series> some of them parent some of them children. Would appreciate a nudge in the right direction.

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• JAX-WS wsgen and collections of collections: wsgen broken?

  - by ayang

  I've been playing around with "bottom-up" JAX-WS and have come across something odd when running wsgen. If I have a service class that does something like: @WebService public class Foo { public ArrayList<Bar> getBarList(String baz) { ... } } then running wsgen gets me a FooService_schema1.xsd that has something like this: <xs:complexType name="getBarListResponse"> <xs:sequence> <xs:element name="return" type="tns:bar" minOccurs="0" maxOccurs="unbounded"/> </xs:sequence> </xs:complexType> which seems reasonable. However, if I want a collection of collections like: public BarCollection getBarCollection(String baz) { ... } // BarCollection is just a container for an ArrayList<Bar> then the generated schema ends up with stuff like: <xs:complexType name="barCollection"> <xs:sequence/> </xs:complexType> <xs:complexType name="getBookCollectionsResponse"> <xs:sequence> <xs:element name="return" type="tns:barCollection" minOccurs="0" maxOccurs="unbounded"/> </xs:sequence> </xs:complexType> An empty sequence is not what I had in mind at all. My original approach was to go with: public ArrayList<ArrayList<Bar>> getBarLists(String baz) { ... } but that ends up with a big chain of complexTypes that just wind up with an empty sequence at the end as well: <xs:complexType name="getBarListsResponse"> <xs:sequence> <xs:element name="return" type="tns:arrayList" minOccurs="0" maxOccurs="unbounded"/> </xs:sequence> </xs:complexType> <xs:complexType name="arrayList"> <xs:complexContent> <xs:extension base="tns:abstractList"> <xs:sequence/> </xs:extension> </xs:complexContent> </xs:complexType> <xs:complexType name="abstractList" abstract="true"> <xs:complexContent> <xs:extension base="tns:abstractCollection"> <xs:sequence/> </xs:extension> </xs:complexContent> </xs:complexType> <xs:complexType name="abstractCollection" abstract="true"> <xs:sequence/> </xs:complexType> Am I missing something or is this a known hole in wsgen? JAXB? Andy

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• Display an Image using C# in Web Application

  - by Josh

  Hello again, I have a Web Application that I built a C# class in that generates a Report. This report takes nearly 40 seconds to generate because it searches hundreds of folders for certain files. So I was hoping there was a way to display a "Loading.." icon as this report is generating. I have a gif stored in my Images folder that would be perfect. The research that I've done at this point mostly talks about picturebox's and image controls that can hold the image but I was hoping there was just a way of displaying the image above the report while its being created. The Web Application is from a Web ADF Geocortex website and again I created a C# class that generates this report. Below is some code that may help. /// <summary> /// Generates HTML for the current report using the data in /// the given table. /// </summary> /// <param name="reportLayers">The layers to include in the report.</param> /// <returns> public override string GenerateReportHtml(List<ReportLayer> reportLayers) { StringBuilder htmlString = new StringBuilder(); StringWriter stringWriter = new StringWriter(htmlString); HtmlTextWriter writer = new HtmlTextWriter(stringWriter); string holdAPI = ""; List<string> exclusions = GetExcludedFields(); foreach (ReportLayer layer in reportLayers) { string[] strFiles = null; Boolean val = false; if (layer.Layer.Name == "Bottom Hole Location (OP)") writer.RenderBeginTag(HtmlTextWriterTag.P); // <p> writer.RenderBeginTag(HtmlTextWriterTag.Strong); // <strong> writer.Write(layer.Layer.Name); writer.RenderEndTag(); // end </strong> writer.RenderEndTag(); // end </p> writer.WriteBreak(); // <br /> foreach (ReportFeature feature in layer.ReportFeatures) { // each feature will be in a table writer.RenderBeginTag(HtmlTextWriterTag.Table); // <table> foreach (ReportField field in feature.ReportFields) { string fieldName = field.Alias; if (!exclusions.Contains(fieldName)) {

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• Abnormally disconnected TCP sockets and write timeout

  - by James

  Hello I will try to explain the problem in shortest possible words. I am using c++ builder 2010. I am using TIdTCPServer and sending voice packets to a list of connected clients. Everything works ok untill any client is disconnected abnormally, For example power failure etc. I can reproduce similar disconnect by cutting the ethernet connection of a connected client. So now we have a disconnected socket but as you know it is not yet detected at server side so server will continue to try to send data to that client too. But when server try to write data to that disconnected client ...... Write() or WriteLn() HANGS there in trying to write, It is like it is wating for somekind of Write timeout. This hangs the hole packet distribution process as a result creating a lag in data transmission to all other clients. After few seconds "Socket Connection Closed" Exception is raised and data flow continues. Here is the code try { EnterCriticalSection(&SlotListenersCriticalSection); for(int i=0;i<SlotListeners->Count;i++) { try { //Here the process will HANG for several seconds on a disconnected socket ((TIdContext*) SlotListeners->Objects[i])->Connection->IOHandler->WriteLn("Some DATA"); }catch(Exception &e) { SlotListeners->Delete(i); } } }__finally { LeaveCriticalSection(&SlotListenersCriticalSection); } Ok i already have a keep alive mechanism which disconnect the socket after n seconds of inactivity. But as you can imagine, still this mechnism cant sync exactly with this braodcasting loop because this braodcasting loop is running almost all the time. So is there any Write timeouts i can specify may be through iohandler or something ? I have seen many many threads about "Detecting disconnected tcp socket" but my problem is little different, i need to avoid that hangup for few seconds during the write attempt. So is there any solution ? Or should i consider using some different mechanism for such data broadcasting for example the broadcasting loop put the data packet in some kind of FIFO buffer and client threads continuously check for available data and pick and deliver it to themselves ? This way if one thread hangs it will not stop/delay the over all distribution thread. Any ideas please ? Thanks for your time and help. Regards Jams

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• Any thoughts on how to create a true 'punch-out' area in a Sprite?

  - by rhtx

  I've been working on this for awhile, now. You might also call it a 'reverse mask', or an 'inverse mask'. Basically, I'm creating a view window within a display object. I need to allow objects on the stage that are under the window to be able to interact with the mouse. This is similar to a WPF question: http://stackoverflow.com/questions/740994/use-wpf-object-to-punch-hole-in-another, which has a much shorter write-up. I've got a Class called PunchOutShield, which creates a Sprite that covers the stage (or over some desired area). The Sprite's Graphics object is filled using the color and transparency of Flex's modal screen. The result is a screen that looks like the screen which appears behind a modal PopUp. PunchOutShield has a method called punch, which takes two arguments - the first is a Shape object, which defines the shape of the punch-through area; the second is a Point object, which indicates where to position the punch-through area. It took some experimenting, but I found that I can successfully create a punch-out area (i.e. - the modal screen does not display within the bounds of the given Shape). To do this, I set cacheAsBitmap to true on the Sprite that is used to create the modal screen, and also on the Shape object, which is added to the modal screen Sprite's displayList. If I set the blend mode of the Shape to ERASE, a completely transparent area is created in the modal screen. So far, great. The problem is that Shape does not subclass InteractiveObject, so there is no way to set mouseEnabled = false on it. And so, it prevents interaction between the mouse and any objects that are visible through the punch-out area. On top of that, InteractiveObject isn't available to look at, so I can't see if there is a way to borrow what it's doing to provide the mouseEnabled functionality and apply it to a subclass of Shape. I've tried using another Sprite object, rather than a Shape object, but the blending doesn't work out correctly. I'm not sure why there is a difference, but the Shape object seems to somehow combine with the parenting Sprite, allowing the ERASE blendMode to effect the desired punch-out visual appearance. It wouldn't be the end of the world if I had to draw up the screen with a series of rectangles so that the punch-out area was just simply not drawn, but that approach won't work if the punch-out area is complex. Or round. Any thoughts on this approach, or on an alternative approach?

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• General workflow to allow multiple OpenIDs to be associated with one app account

  - by BobTodd

  I have a (typical?) scenario: that my app's users can use multiple openids mapped to one app account (like stackoverflow). For me the unique thing on the account is the email address, so this binds openids to the profile. Question is, how to allow a user to start using a second openid once one is setup. I am asking as I have read that it is a security hole to allow automatic account openid syncing simply based on the provider-supplied email address as someone could easily spoof someone's email address to create a spoof openid and falsely access the account (how I am not sure) - although this seems to be exactly how stack operates. See options a. and b. below. Problem for me with a. is what happens if the original openid no longer works for whatever reason - how would you set-up a new openid? Would b. be more acceptable if we used email verification? Does anyone have an article detailing a "standard" way (set of user stories) for this - it seems to be an increasingly popular way to authenticate. I have tried to detail this in a rough decision tree... 1. My Site > authentication landing page - user chooses an openid (facebook, google, myopenid etc), redirection > 2. Provider site returns with token (includes user registering a new openid, logging in or is already logged in to Provider site) 3. My Site > use token id to lookup user 3.1 Profile exists? Yes > authenticate. ends. No > 3.1.1 was email address supplied by provider? Yes > lookup user by email address 3.1.1.1 Profile exists? Yes > a. error message - please login with existing openid and associate this openid (from special page) Yes > b. or associate this openid with existing profile automatically. authenticate. ends. No > Register profile. With registration email address follow 3.1.1, except this time where email is unique, we will associate openid. ends

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• C++ linked list based tree structure. Sanely move nodes between lists.

  - by krunk

  The requirements: Each Node in the list must contain a reference to its previous sibling Each Node in the list must contain a reference to its next sibling Each Node may have a list of child nodes Each child Node must have a reference to its parent node Basically what we have is a tree structure of arbitrary depth and length. Something like: -root(NULL) --Node1 ----ChildNode1 ------ChildOfChild --------AnotherChild ----ChildNode2 --Node2 ----ChildNode1 ------ChildOfChild ----ChildNode2 ------ChildOfChild --Node3 ----ChildNode1 ----ChildNode2 Given any individual node, you need to be able to either traverse its siblings. the children, or up the tree to the root node. A Node ends up looking something like this: class Node { Node* previoius; Node* next; Node* child; Node* parent; } I have a container class that stores these and provides STL iterators. It performs your typical linked list accessors. So insertAfter looks like: void insertAfter(Node* after, Node* newNode) { Node* next = after->next; after->next = newNode; newNode->previous = after; next->previous = newNode; newNode->next = next; newNode->parent = after->parent; } That's the setup, now for the question. How would one move a node (and its children etc) to another list without leaving the previous list dangling? For example, if Node* myNode exists in ListOne and I want to append it to listTwo. Using pointers, listOne is left with a hole in its list since the next and previous pointers are changed. One solution is pass by value of the appended Node. So our insertAfter method would become: void insertAfter(Node* after, Node newNode); This seems like an awkward syntax. Another option is doing the copying internally, so you'd have: void insertAfter(Node* after, const Node* newNode) { Node *new_node = new Node(*newNode); Node* next = after->next; after->next = new_node; new_node->previous = after; next->previous = new_node; new_node->next = next; new_node->parent = after->parent; } Finally, you might create a moveNode method for moving and prevent raw insertion or appending of a node that already has been assigned siblings and parents. // default pointer value is 0 in constructor and a operator bool(..) // is defined for the Node bool isInList(const Node* node) const { return (node->previous || node->next || node->parent); } // then in insertAfter and friends if(isInList(newNode) // throw some error and bail I thought I'd toss this out there and see what folks came up with.

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• Connection between Properties of Entities in Data Oriented Design

  - by sharethis

  I want to start with an example illustrating my question. The following way it is done in the most games. class car { vec3 position; vec3 rotation; mesh model; imge texture; void move(); // modify position and rotation void draw(); // use model, texture, ... }; vector<car> cars; for(auto i = cars.begin(); i != cars.end(); ++i) { i->move(); i->draw(); } Data oriented design means to process the same calculation on the hole batch of data at once. This way it takes more advantage out of the processor cache. struct movedata { vec3 position; vec3 rotation; }; struct drawdata { mesh model; imge texture; }; vector<movedata> movedatas; vector<drawdata> drawdatas; for(auto i = movedatas.begin(); i != movedatas.end(); ++i) { // modify position and rotation } for(auto i = drawdatas.begin(); i != drawdatas.end(); ++i) { // use model, texture, ... } But there comes a point where you need to find other properties according to an entity. For example if the car crashes, I do not need the drawdata and the movedata any more. So I need to delete the entries of this entity in all vectors. The entries are not linked by code. So my question is the following. How are properties of the same entity conceptually linked in a data oriented design?

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• How Hacker Can Access VPS CentOS 6 content?

  - by user2118559

  Just want to understand. Please, correct mistakes and write advices Hacker can access to VPS: 1. Through (using) console terminal, for example, using PuTTY. To access, hacker need to know port number, username and password. Port number hacker can know scanning open ports and try to login. The only way to login as I understand need to know username and password. To block (make more difficult) port scanning, need to use iptables configure /etc/sysconfig/iptables. I followed this https://www.digitalocean.com/community/articles/how-to-setup-a-basic-ip-tables-configuration-on-centos-6 tutorial and got *nat :PREROUTING ACCEPT [87:4524] :POSTROUTING ACCEPT [77:4713] :OUTPUT ACCEPT [77:4713] COMMIT *mangle :PREROUTING ACCEPT [2358:200388] :INPUT ACCEPT [2358:200388] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [2638:477779] :POSTROUTING ACCEPT [2638:477779] COMMIT *filter :INPUT DROP [1:40] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [339:56132] -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT -A INPUT -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG NONE -j DROP -A INPUT -p tcp -m tcp ! --tcp-flags FIN,SYN,RST,ACK SYN -m state --state NEW -j DROP -A INPUT -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG FIN,SYN,RST,PSH,ACK,URG -j DROP -A INPUT -i lo -j ACCEPT -A INPUT -p tcp -m tcp --dport 80 -j ACCEPT -A INPUT -p tcp -m tcp --dport 110 -j ACCEPT -A INPUT -p tcp -m tcp --dport 22 -j ACCEPT -A INPUT -s 11.111.11.111/32 -p tcp -m tcp --dport 22 -j ACCEPT -A INPUT -p tcp -m tcp --dport 21 -j ACCEPT -A INPUT -s 11.111.11.111/32 -p tcp -m tcp --dport 21 -j ACCEPT COMMIT Regarding ports that need to be opened. If does not use ssl, then seems must leave open port 80 for website. Then for ssh (default 22) and for ftp (default 21). And set ip address, from which can connect. So if hacker uses other ip address, he can not access even knowing username and password? Regarding emails not sure. If I send email, using Gmail (Send mail as: (Use Gmail to send from your other email addresses)), then port 25 not necessary. For incoming emails at dynadot.com I use Email Forwarding. Does it mean that emails “does not arrive to VPS” (before arriving to VPS, emails are forwarded, for example to Gmail)? If emails does not arrive to VPS, then seems port 110 also not necessary. If use only ssl, must open port 443 and close port 80. Do not understand regarding port 3306 In PuTTY with /bin/netstat -lnp see Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 0.0.0.0:3306 0.0.0.0:* LISTEN 992/mysqld As understand it is for mysql. But does not remember that I have opened such port (may be when installed mysql, the port is opened automatically?). Mysql is installed on the same server, where all other content. Need to understand regarding port 3306 2. Also hacker may be able access console terminal through VPS hosting provider Control Panel (serial console emergency access). As understand only using console terminal (PuTTY, etc.) can make “global” changes (changes that can not modify with ftp). 3. Hacker can access to my VPS exploiting some hole in my php code and uploading, for example, Trojan. Unfortunately, faced situation that VPS was hacked. As understand it was because I used ZPanel. On VPS ( \etc\zpanel\panel\bin) ) found one php file, that was identified as Trojan by some virus scanners (at virustotal.com). Experimented with the file on local computer (wamp). And appears that hacker can see all content of VPS, rename, delete, upload etc. From my opinion, if in PuTTY use command like chattr +i /etc/php.ini then hacker could not be able to modify php.ini. Is there any other way to get into VPS?

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• Week in Geek: LastPass Rescues Xmarks Edition

  - by Asian Angel

  This week we learned how to breathe new life into an aging Windows Mobile 6.x device, use filters in Photoshop, backup and move VirtualBox machines, use the BitDefender Rescue CD to clean an infected PC, and had fun setting up a pirates theme on our computers. Photo by _nash. Weekly Feature Do you love using the Faenza icon set on your Ubuntu system but feel that there are a few much needed icons missing (or you desire a different version of a particular icon)? Then you may want to take a look at the Faenza Variants icon pack. The icons are available in the following sizes: 16px, 22px, 32px, 48px and scalable sizes. Photo by Asian Angel. Faenza Variants Random Geek Links Another week with extra link goodness to help keep you on top of the news. Photo by Asian Angel. LastPass acquires Xmarks, premium service announced Xmarks announced that it has been acquired by LastPass, a cross-platform password management service. This also means that Xmarks is now in transition from a “free” to a “freemium” business model. WikiLeaks reappears on European Net domains WikiLeaks has re-emerged on a Swiss Internet domain followed by domains in Germany, Finland, and the Netherlands, sidestepping a move that had in effect taken the controversial site off the Internet. Iran: Yes, Stuxnet hurt our nuclear program The Stuxnet worm got some big play from Iranian President Mahmoud Ahmadinejad, who acknowledged that the malware dinged his nuclear program. More Windows Rogues than Just AV – Fake Defragmenter Check Disk Don’t think for a second that rogues are limited to scareware, because as so-called products such as “System Defragmenter”, “Scan Disk” “Check Disk” prove, they’re not. Internet Explorer’s Protected Mode can be bypassed Researchers from Verizon Business have now described a way of bypassing Protected Mode in IE 7 and 8 in order to gain access to user accounts. Can you really see who viewed your Facebook profile? Rogue application spreads virally Once again, a rogue application is spreading virally between Facebook users pretending to offer you a way of seeing who has viewed your profile. More holes in Palm’s WebOS Researchers Orlando Barrera and Daniel Herrera, who both work for security firm SecTheory, have discovered a gaping security hole in Palm’s WebOS smartphone operating system. Next-gen banking Trojans hit APAC With the proliferation of banking Trojans, Web and smartphone users of online banking services have to be on constant alert to avoid falling prey to fraud schemes, warned Etay Maor, project manager for RSA Fraud Action. AVG update cripples 64-bit computers A signature update automatically deployed by the AVG virus scanner Thursday has crippled numerous computers. Article includes link to forums to fix computers affected after a restart. Congress moves to outlaw ‘mystery charges’ for Web shoppers Legislation that makes it illegal for Web merchants and so-called post-transaction marketers to charge credit cards without the card owners’ say-so came closer to becoming law this week. Ballmer Set to “Look Into” Windows Home Server Drive Extender Fiasco Tuesday’s announcement from Microsoft regarding the removal of Drive Extender from Windows Home Server has sent shock waves across the web. Google tweaks search recipe to ding scam artists Google has changed its search algorithm to penalize sites deemed to provide an “extremely poor user experience” following a New York Times story on a merchant who justified abusive behavior towards customers as a search-engine optimization tactic. Geek Video of the Week Watch as our two friends debate back and forth about the early adoption of new technology through multiple time periods (Stone Age to the far future). Will our reluctant friend finally succumb to the temptation? Photo by CollegeHumor. Early Adopters Through History Random TinyHacker Links Fix Issues in Windows 7 Using Reliability Monitor Learn how to analyze Windows 7 errors and then fix them using the built-in reliability monitor. Learn About IE Tab Groups Tab groups is a useful feature in IE 8. Here’s a detailed guide to what it is all about. Google’s Book Helps You Learn About Browsers and Web A cool new online book by the Google Chrome team on browsers and the web. TrustPort Internet Security 2011 – Good Security from a Less Known Provider TrustPort is not exactly a well-known provider of security solutions. At least not in the consumer space. This review tests in detail their latest offering. How the World is Using Cell phones An infographic showing the shocking demographics of cell phone use. Super User Questions See the great answers to these questions from Super User. I am unable to access my C drive. It says it is unable to display current owner. List of Windows special directories/shortcuts like ‘%TEMP%’ Is using multiple passes for wiping a disk really necessary? How can I view two files side by side in Notepad++ Is there any tool that automatically puts screenshots to my Dropbox? How-To Geek Weekly Article Recap Look through our hottest articles from this past week at How-To Geek. How to Create a Software RAID Array in Windows 7 9 Alternatives for Windows Home Server’s Drive Extender Why Doesn’t Disk Cleanup Delete Everything from the Temp Folder? Ask the Readers: How Much Do You Customize Your Operating System? How to Upload Really Large Files to SkyDrive, Dropbox, or Email One Year Ago on How-To Geek Enjoy reading through these awesome articles from one year ago. How To Upgrade from Vista to Windows 7 Home Premium Edition How To Fix No Aero Transparency in Windows 7 Troubleshoot Startup Problems with Startup Repair Tool in Windows 7 & Vista Rename the Guest Account in Windows 7 for Enhanced Security Disable Error Reporting in XP, Vista, and Windows 7 The Geek Note That wraps things up here for this week. Regardless of the weather wherever you may be, we hope that you have an opportunity to get outside and have some fun! Remember to keep sending those great tips in to us at [email protected]. Photo by Tony the Misfit. Latest Features How-To Geek ETC The How-To Geek Guide to Learning Photoshop, Part 8: Filters Get the Complete Android Guide eBook for Only 99 Cents [Update: Expired] Improve Digital Photography by Calibrating Your Monitor The How-To Geek Guide to Learning Photoshop, Part 7: Design and Typography How to Choose What to Back Up on Your Linux Home Server How To Harmonize Your Dual-Boot Setup for Windows and Ubuntu Hang in There Scrat! – Ice Age Wallpaper How Do You Know When You’ve Passed Geek and Headed to Nerd? On The Tip – A Lamborghini Theme for Chrome and Iron What if Wile E. Coyote and the Road Runner were Human? [Video] Peaceful Winter Cabin Wallpaper Store Tabs for Later Viewing in Opera with Tab Vault

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• Too Many Kittens To Juggle At Once

  - by Bil Simser

  Ahh, the Internet. That crazy, mixed up place where one tweet turns into a conversation between dozens of people and spawns a blogpost. This is the direct result of such an event this morning. It started innocently enough, with this: Then followed up by a blog post by Joel here. In the post, Joel introduces us to the term Business Solutions Architect with mad skillz like InfoPath, Access Services, Excel Services, building Workflows, and SSRS report creation, all while meeting the business needs of users in a SharePoint environment. I somewhat disagreed with Joel that this really wasn’t a new role (at least IMHO) and that a good Architect or BA should really be doing this job. As Joel pointed out when you’re building a SharePoint team this kind of role is often overlooked. Engineers might be able to build workflows but is the right workflow for the right problem? Michael Pisarek wrote about a SharePoint Business Architect a few months ago and it’s a pretty solid assessment. Again, I argue you really shouldn’t be looking for roles that don’t exist and I don’t suggest anyone create roles to hire people to fill them. That’s basically creating a solution looking for problems. Michael’s article does have some great points if you’re lost in the quagmire of SharePoint duties though (and I especially like John Ross’ quote “The coolest shit is worthless if it doesn’t meet business needs”). SharePoinTony summed it up nicely with “SharePoint Solutions knowledge is both lacking and underrated in most environments. Roles help”. Having someone on the team who can dance between a business user and a coder can be difficult. Remember the idea of telling something to someone and them passing it on to the next person. By the time the story comes round the circle it’s a shadow of it’s former self with little resemblance to the original tale. This is very much business requirements as they’re told by the user to a business analyst, written down on paper, read by an architect, tuned into a solution plan, and implemented by a developer. Transformations between what was said, what was heard, what was written down, and what was developed can be distant cousins. Not everyone has the skill of communication and even less have negotiation skills to suit the SharePoint platform. Negotiation is important because not everything can be (or should be) done in SharePoint. Sometimes it’s just not appropriate to build it on the SharePoint platform but someone needs to know enough about the platform and what limitations it might have, then communicate that (and/or negotiate) with a customer or user so it’s not about “You can’t have this” to “Let’s try it this way”. Visualize the possible instead of denying the impossible. So what is the right SharePoint team? My cromag brain came with a fairly simpleton answer (and I’m sure people will just say this is a cop-out). The perfect SharePoint team is just enough people to do the job that know the technology and business problem they’re solving. Bridge the gap between business need and technology platform and you have an architect. Communicate the needs of the business effectively so the entire team understands it and you have a business analyst. Can you get this with full time workers? Maybe but don’t expect miracles out of the gate. Also don’t take a consultant’s word as gospel. Some consultants just don’t have the diversity of the SharePoint platform to be worth their value so be careful. You really need someone who knows enough about SharePoint to be able to validate a consultants knowledge level. This is basically try for any consultant, not just a SharePoint one. Specialization is good and needed. A good, well-balanced SharePoint team is one of people that can solve problems with work with the technology, not against it. Having a top developer is great, but don’t rely on them to solve world hunger if they can’t communicate very well with users. An expert business analyst might be great at gathering requirements so the entire team can understand them, but if it means building 100% custom solutions because they don’t fit inside the SharePoint boundaries isn’t of much value. Just repeat. There is no silver bullet. There is no silver bullet. There is no silver bullet. A few people pointed out Nick Inglis’ article Excluding The Information Professional In SharePoint. It’s a good read too and hits home that maybe some developers and IT pros need some extra help in the information space. If you’re in an organization that needs labels on people, come up with something everyone understands and go with it. If that’s Business Solutions Architect, SharePoint Advisor, or Guy Who Knows A Lot About Portals, make it work for you. We all wish that one person could master all that is SharePoint but we also know that doesn’t scale very well and you quickly get into the hit-by-a-bus syndrome (with the organization coming to a full crawl when the guy or girl goes on vacation, gets sick, or pops out a baby). There are too many gaps in SharePoint knowledge to have any one person know it all and too many kittens to juggle all at once. We like to consider ourselves experts in our field, but trying to tackle too many roles at once and we end up being mediocre jack of all trades, master of none. Don't fall into this pit. It's a deep, dark hole you don't want to try to claw your way out of. Trust me. Been there. Done that. Got the t-shirt. In the end I don’t disagree with Joel. SharePoint is a beast and not something that should be taken on by newbies. If you just read “Teach Yourself SharePoint in 24 Hours” and want to go build your corporate intranet or the next killer business solution with all your new found knowledge plan to pony up consultant dollars a few months later when everything goes to Hell in a handbasket and falls over. I’m not saying don’t build solutions in SharePoint. I’m just saying that building effective ones takes skill like any craft and not something you can just cobble together with a little bit of cursory knowledge. Thanks to *everyone* who participated in this tweet rush. It was fun and educational.

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• techniques for an AI for a highly cramped turn-based tactics game

  - by Adam M.

  I'm trying to write an AI for a tactics game in the vein of Final Fantasy Tactics or Vandal Hearts. I can't change the game rules in any way, only upgrade the AI. I have experience programming AI for classic board games (basically minimax and its variants), but I think the branching factor is too great for the approach to be reasonable here. I'll describe the game and some current AI flaws that I'd like to fix. I'd like to hear ideas for applicable techniques. I'm a decent enough programmer, so I only need the ideas, not an implementation (though that's always appreciated). I'd rather not expend effort chasing (too many) dead ends, so although speculation and brainstorming are good and probably helpful, I'd prefer to hear from somebody with actual experience solving this kind of problem. For those who know it, the game is the land battle mini-game in Sid Meier's Pirates! (2004) and you can skim/skip the next two paragraphs. For those who don't, here's briefly how it works. The battle is turn-based and takes place on a 16x16 grid. There are three terrain types: clear (no hindrance), forest (hinders movement, ranged attacks, and sight), and rock (impassible, but does not hinder attacks or sight). The map is randomly generated with roughly equal amounts of each type of terrain. Because there are many rock and forest tiles, movement is typically very cramped. This is tactically important. The terrain is not flat; higher terrain gives minor bonuses. The terrain is known to both sides. The player is always the attacker and the AI is always the defender, so it's perfectly valid for the AI to set up a defensive position and just wait. The player wins by killing all defenders or by getting a unit to the city gates (a tile on the other side of the map). There are very few units on each side, usually 4-8. Because of this, it's crucial not to take damage without gaining some advantage from it. Units can take multiple actions per turn. All units on one side move before any units on the other side. Order of execution is important, and interleaving of actions between units is often useful. Units have melee and ranged attacks. Melee attacks vary widely in strength; ranged attacks have the same strength but vary in range. The main challenges I face are these: Lots of useful move combinations start with a "useless" move that gains no immediate advantage, or even loses advantage, in order to set up a powerful flank attack in the future. And, since the player units are stronger and have longer range, the AI pretty much always has to take some losses before they can start to gain kills. The AI must be able to look ahead to distinguish between sacrificial actions that provide a future benefit and those that don't. Because the terrain is so cramped, most of the tactics come down to achieving good positioning with multiple units that work together to defend an area. For instance, two defenders can often dominate a narrow pass by positioning themselves so an enemy unit attempting to pass must expose itself to a flank attack. But one defender in the same pass would be useless, and three units can defend a slightly larger pass. Etc. The AI should be able to figure out where the player must go to reach the city gates and how to best position its few units to cover the approaches, shifting, splitting, or combining them appropriately as the player moves. Because flank attacks are extremely deadly (and engineering flank attacks is key to the player strategy), the AI should be competent at moving its units so that they cover each other's flanks unless the sacrifice of a unit would give a substantial benefit. They should also be able to force flank attacks on players, for instance by threatening a unit from two different directions such that responding to one threat exposes the flank to the other. The AI should attack if possible, but sometimes there are no good ways to approach the player's position. In that case, the AI should be able to recognize this and set up a defensive position of its own. But the AI shouldn't be vulnerable to a trivial exploit where the player repeatedly opens and closes a hole in his defense and shoots at the AI as it approaches and retreats. That is, the AI should ideally be able to recognize that the player is capable of establishing a solid defense of an area, even if the defense is not currently in place. (I suppose if a good unit allocation algorithm existed, as needed for the second bullet point, the AI could run it on the player units to see where they could defend.) Because it's important to choose a good order of action and interleave actions between units, it's not as simple as just finding the best move for each unit in turn. All of these can be accomplished with a minimax search in theory, but the search space is too large, so specialized techniques are needed. I thought about techniques such as influence mapping, but I don't see how to use the technique to great effect. I thought about assigning goals to the units. This can help them work together in some limited way, and the problem of "how do I accomplish this goal?" is easier to solve than "how do I win this battle?", but assigning good goals is a hard problem in itself, because it requires knowing whether the goal is achievable and whether it's a good use of resources. So, does anyone have specific ideas for techniques that can help cleverize this AI? Update: I found a related question on Stackoverflow: http://stackoverflow.com/questions/3133273/ai-for-a-final-fantasy-tactics-like-game The selected answer gives a decent approach to choosing between alternative actions, but it doesn't seem to have much ability to look into the future and discern beneficial sacrifices from wasteful ones. It also focuses on a single unit at a time and it's not clear how it could be extended to support cooperation between units in defending or attacking.

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• Visual Studio 2010 Productivity Tips and Tricks&ndash;Part 1: Extensions

  - by ToStringTheory

  I don’t know about you, but when it comes to development, I prefer my environment to be as free of clutter as possible.  It may surprise you to know that I have tried ReSharper, and did not like it, for the reason that I stated above.  In my opinion, it had too much clutter.  Don’t get me wrong, there were a couple of features that I did like about it (inversion of if blocks, code feedback), but for the most part, I actually felt that it was slowing me down. Introduction Another large factor besides intrusiveness/speed in my choice to dislike ReSharper would probably be that I have become comfortable with my current setup and extensions.  I believe I have a good collection, and am quite happy with what I can accomplish in a short amount of time.  I figured that I would share some of my tips/findings regarding Visual Studio productivity here, and see what you had to say. The first section of things that I would like to cover, are Visual Studio Extensions.  In case you have been living under a rock for the past several years, Extensions are available under the Tools menu in Visual Studio: The extension manager enables integrated access to the Microsoft Visual Studio Gallery online with access to a few thousand different extensions.  I have tried many extensions, but for reasons of lack reliability, usability, or features, have uninstalled almost all of them.  However, I have come across several that I find I can not do without anymore: NuGet Package Manager (Microsoft) Perspectives (Adam Driscoll) Productivity Power Tools (Microsoft) Web Essentials (Mads Kristensen) Extensions NuGet Package Manager To be honest, I debated on whether or not to put this in here.  Most people seem to have it, however, there was a time when I didn’t, and was always confused when blogs/posts would say to right click and “Add Package Reference…” which with one of the latest updates is now “Manage NuGet Packages”.  So, if you haven’t downloaded the NuGet Package Manager yet, or don’t know what it is, I would highly suggest downloading it now! Features Simply put, the NuGet Package Manager gives you a GUI and command line to access different libraries that have been uploaded to NuGet. Some of its features include: Ability to search NuGet for packages via the GUI, with information in the detail bar on the right. Quick access to see what packages are in a solution, and what packages have updates available, with easy 1-click updating. If you download a package that requires references to work on other NuGet packages, they will be downloaded and referenced automatically. Productivity Tip If you use any type of source control in Visual Studio as well as using NuGet packages, be sure to right-click on the solution and click "Enable NuGet Package Restore". What this does is add a NuGet package to the solution so that it will be checked in along side your solution, as well as automatically grab packages from NuGet on build if needed. This is an extremely simple system to use to manage your package references, instead of having to manually go into TFS and add the Packages folder. Perspectives I can't stand developing with just one monitor. Especially if it comes to debugging. The great thing about Visual Studio 2010, is that all of the panels and windows are floatable, and can dock to other screens. The only bad thing is, I don't use the same toolset with everything that I am doing. By this, I mean that I don't use all of the same windows for debugging a web application, as I do for coding a WPF application. Only thing is, Visual Studio doesn't save the screen positions for all of the undocked windows. So, I got curious one day and decided to check and see if there was an extension to help out. This is where I found Perspectives. Features Perspectives gives you the ability to configure window positions across any or your monitors, and then to save the positions in a profile. Perspectives offers a Panel to manage different presets/favorites, and a toolbar to add to the toolbars at the top of Visual Studio. Ability to 'Favorite' a profile to add it to the perspectives toolbar. Productivity Tip Take the time to setup profiles for each of your scenarios - debugging web/winforms/xaml, coding, maintenance, etc. Try to remember to use the profiles for a few days, and at the end of a week, you may find that your productivity was never better. Productivity Power Tools Ah, the Productivity Power Tools... Quite possibly one of my most used extensions, if not my most used. The tool pack gives you a variety of enhancements ranging from key shortcuts, interface tweaks, and completely new features to Visual Studio 2010. Features I don't want to bore you with all of the features here, so here are my favorite: Quick Find - Unobtrusive search box in upper-right corner of the code window. Great for searching in general, especially in a file. Solution Navigator - The 'Solution Explorer' on steroids. Easy to search for files, see defined members/properties/methods in files, and my favorite feature is the 'set as root' option. Updated 'Add Reference...' Dialog - This is probably my favorite enhancement period... The 'Add Reference...' dialog redone in a manner that resembles the Extension/Package managers. I especially love the ability to search through all of the references. "Ctrl - Click" for Definition - I am still getting used to this as I usually try to use my keyboard for everything, but I love the ability to hold Ctrl and turn property/methods/variables into hyperlinks, that you click on to see their definitions. Great for travelling down a rabbit hole in an application to research problems. While there are other commands/utilities, I find these to be the ones that I lean on the most for the usefulness. Web Essentials If you have do any type of web development in ASP .Net, ASP .Net MVC, even HTML, I highly suggest grabbing the Web Essentials right NOW! This extension alone is great for productivity in web development, and greatly decreases my development time on new features. Features Some of its best features include: CSS Previews - I say 'previews' because of the multiple kinds of previews in CSS that you get font-family, color, background/background-image previews. This is great for just tweaking UI slightly in different ways and seeing how they look in the CSS window at a glance. Live Preview - One word - awesome! This goes well with my multi-monitor setup. I put the site on one monitor in a Live Preview panel, and then as I make changes to CSS/cshtml/aspx/html, the preview window will update with each save/build automatically. For CSS, you can even turn on live-update, so as you are tweaking CSS, the style changes in real time. Great for tweaking colors or font-sizes. Outlining - Small, but I like to be able to collapse regions/declarations that are in the way of new work, or are just distracting. Commenting Shortcuts - I don't know why it wasn't included by default, but it is nice to have the key shortcuts for commenting working in the CSS editor as well. Productivity Tip When working on a site, hit CTRL-ALT-ENTER to launch the Live Preview window. Dock it to another monitor. When you make changes to the document/css, just save and glance at the other monitor. No need to alt tab, then alt tab before continuing editing. Conclusion These extensions are only the most useful and least intrusive - ones that I use every day. The great thing about Visual Studio 2010 is the extensibility options that it gives developers to utilize. Have an extension that you use that isn't intrusive, but isn't listed here? Please, feel free to comment. I love trying new things, and am always looking for new additions to my toolset of the most useful. Finally, please keep an eye out for Part 2 on key shortcuts in Visual Studio. Also, if you are visiting my site (http://tostringtheory.com || http://geekswithblogs.net/tostringtheory) from an actual browser and not a feed, please let me know what you think of the new styling!

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• Metrics - A little knowledge can be a dangerous thing (or 'Why you're not clever enough to interpret metrics data')

  - by Jason Crease

  At RedGate Software, I work on a .NET obfuscator  called SmartAssembly.  Various features of it use a database to store various things (exception reports, name-mappings, etc.) The user is given the option of using either a SQL-Server database (which requires them to have Microsoft SQL Server), or a Microsoft Access MDB file (which requires nothing). MDB is the default option, but power-users soon switch to using a SQL Server database because it offers better performance and data-sharing. In the fashionable spirit of optimization and metrics, an obvious product-management question is 'Which is the most popular? SQL Server or MDB?' We've collected data about this fact, using our 'Feature-Usage-Reporting' technology (available as part of SmartAssembly) and more recently our 'Application Metrics' technology: Parameter Number of users % of total users Number of sessions Number of usages SQL Server 28 19.0 8115 8115 MDB 114 77.6 1449 1449 (As a disclaimer, please note than SmartAssembly has far more than 132 users . This data is just a selection of one build) So, it would appear that SQL-Server is used by fewer users, but more often. Great. But here's why these numbers are useless to me: Only the original developers understand the data What does a single 'usage' of 'MDB' mean? Does this happen once per run? Once per option change? On clicking the 'Obfuscate Now' button? When running the command-line version or just from the UI version? Each question could skew the data 10-fold either way, and the answers only known by the developer that instrumented the application in the first place. In other words, only the original developer can interpret the data - product-managers cannot interpret the data unaided. Most of the data is from uninterested users About half of people who download and run a free-trial from the internet quit it almost immediately. Only a small fraction use it sufficiently to make informed choices. Since the MDB option is the default one, we don't know how many of those 114 were people CHOOSING to use the MDB, or how many were JUST HAPPENING to use this MDB default for their 20-second trial. This is a problem we see across all our metrics: Are people are using X because it's the default or are they using X because they want to use X? We need to segment the data further - asking what percentage of each percentage meet our criteria for an 'established user' or 'informed user'. You end up spending hours writing sophisticated and dubious SQL queries to segment the data further. Not fun. You can't find out why they used this feature Metrics can answer the when and what, but not the why. Why did people use feature X? If you're anything like me, you often click on random buttons in unfamiliar applications just to explore the feature-set. If we listened uncritically to metrics at RedGate, we would eliminate the most-important and more-complex features which people actually buy the software for, leaving just big buttons on the main page and the About-Box. "Ah, that's interesting!" rather than "Ah, that's actionable!" People do love data. Did you know you eat 1201 chickens in a lifetime? But just 4 cows? Interesting, but useless. Often metrics give you a nice number: '5.8% of users have 3 or more monitors' . But unless the statistic is both SUPRISING and ACTIONABLE, it's useless. Most metrics are collected, reviewed with lots of cooing. and then forgotten. Unless a piece-of-data could change things, it's useless collecting it. People get obsessed with significance levels The first things that lots of people do with this data is do a t-test to get a significance level ("Hey! We know with 99.64% confidence that people prefer SQL Server to MDBs!") Believe me: other causes of error/misinterpretation in your data are FAR more significant than your t-test could ever comprehend. Confirmation bias prevents objectivity If the data appears to match our instinct, we feel satisfied and move on. If it doesn't, we suspect the data and dig deeper, plummeting down a rabbit-hole of segmentation and filtering until we give-up and move-on. Data is only useful if it can change our preconceptions. Do you trust this dodgy data more than your own understanding, knowledge and intelligence?  I don't. There's always multiple plausible ways to interpret/action any data Let's say we segment the above data, and get this data: Post-trial users (i.e. those using a paid version after the 14-day free-trial is over): Parameter Number of users % of total users Number of sessions Number of usages SQL Server 13 9.0 1115 1115 MDB 5 4.2 449 449 Trial users: Parameter Number of users % of total users Number of sessions Number of usages SQL Server 15 10.0 7000 7000 MDB 114 77.6 1000 1000 How do you interpret this data? It's one of: Mostly SQL Server users buy our software. People who can't afford SQL Server tend to be unable to afford or unwilling to buy our software. Therefore, ditch MDB-support. Our MDB support is so poor and buggy that our massive MDB user-base doesn't buy it.  Therefore, spend loads of money improving it, and think about ditching SQL-Server support. People 'graduate' naturally from MDB to SQL Server as they use the software more. Things are fine the way they are. We're marketing the tool wrong. The large number of MDB users represent uninformed downloaders. Tell marketing to aggressively target SQL Server users. To choose an interpretation you need to segment again. And again. And again, and again. Opting-out is correlated with feature-usage Metrics tends to be opt-in. This skews the data even further. Between 5% and 30% of people choose to opt-in to metrics (often called 'customer improvement program' or something like that). Casual trial-users who are uninterested in your product or company are less likely to opt-in. This group is probably also likely to be MDB users. How much does this skew your data by? Who knows? It's not all doom and gloom. There are some things metrics can answer well. Environment facts. How many people have 3 monitors? Have Windows 7? Have .NET 4 installed? Have Japanese Windows? Minor optimizations.  Is the text-box big enough for average user-input? Performance data. How long does our app take to start? How many databases does the average user have on their server? As you can see, questions about who-the-user-is rather than what-the-user-does are easier to answer and action. Conclusion Use SmartAssembly. If not for the metrics (called 'Feature-Usage-Reporting'), then at least for the obfuscation/error-reporting. Data raises more questions than it answers. Questions about environment are the easiest to answer.

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• Recursion in the form of a Recursive Func&lt;T, T&gt;

  - by ToStringTheory

  I gotta admit, I am kind of surprised that I didn’t realize I could do this sooner.  I recently had a problem which required a recursive function call to come up with the answer.  After some time messing around with a recursive method, and creating an API that I was not happy with, I was able to create an API that I enjoy, and seems intuitive. Introduction To bring it to a simple example, consider the summation to n: A mathematically identical formula is: In a .NET function, this can be represented by a function: Func<int, int> summation = x => x*(x+1)/2 Calling summation with an input integer will yield the summation to that number: var sum10 = summation(4); //sum10 would be equal to 10 But what if I wanted to get a second level summation…  First some to n, and then use that argument as the input to the same function, to find the second level summation: So as an easy example, calculate the summation to 3, which yields 6.  Then calculate the summation to 6 which yields 21. Represented as a mathematical formula - So what if I wanted to represent this as .NET functions.  I can always do: //using the summation formula from above var sum3 = summation(3); //sets sum3 to 6 var sum3_2 = summation(sum3); //sets sum3 to 21 I could always create a while loop to perform the calculations too: Func<int, int> summation = x => x*(x+1)/2; //for the interests of a smaller example, using shorthand int sumResultTo = 3; int level = 2; while(level-- > 0) { sumResultTo = summation(sumResultTo); } //sumResultTo is equal to 21 now. Or express it as a for-loop, method calls, etc…  I really didn’t like any of the options that I tried.  Then it dawned on me – since I was using a Func<T, T> anyways, why not use the Func’s output from one call as the input as another directly. Some Code So, I decided that I wanted a recursion class.  Something that I would be generic and reusable in case I ever wanted to do something like this again. It is limited to only the Func<T1, T2> level of Func, and T1 must be the same as T2. The first thing in this class is a private field for the function: private readonly Func<T, T> _functionToRecurse; So, I since I want the function to be unchangeable, I have defined it as readonly.  Therefore my constructor looks like: public Recursion(Func<T, T> functionToRecurse) { if (functionToRecurse == null) { throw new ArgumentNullException("functionToRecurse", "The function to recurse can not be null"); } _functionToRecurse = functionToRecurse; } Simple enough.  If you have any questions, feel free to post them in the comments, and I will be sure to answer them. Next, I want enough. If be able to get the result of a function dependent on how many levels of recursion: private Func<T, T> GetXLevel(int level) { if (level < 1) { throw new ArgumentOutOfRangeException("level", level, "The level of recursion must be greater than 0"); } if (level == 1) return _functionToRecurse; return _GetXLevel(level - 1, _functionToRecurse); } So, if you pass in 1 for the level, you get just the Func<T,T> back.  If you say that you want to go deeper down the rabbit hole, it calls a method which accepts the level it is at, and the function which it needs to use to recurse further: private Func<T, T> _GetXLevel(int level, Func<T, T> prevFunc) { if (level == 1) return y => prevFunc(_functionToRecurse(y)); return _GetXLevel(level - 1, y => prevFunc(_functionToRecurse(y))); } That is really all that is needed for this class. If I exposed the GetXLevel function publicly, I could use that to get the function for a level, and pass in the argument..  But I wanted something better.  So, I used the ‘this’ array operator for the class: public Func<T,T> this[int level] { get { if (level < 1) { throw new ArgumentOutOfRangeException("level", level, "The level of recursion must be greater than 0"); } return this.GetXLevel(level); } } So, using the same example above of finding the second recursion of the summation of 3: var summator = new Recursion<int>(x => (x * (x + 1)) / 2); var sum_3_level2 = summator[2](3); //yields 21 You can even find just store the delegate to the second level summation, and use it multiple times: var summator = new Recursion<int>(x => (x * (x + 1)) / 2); var sum_level2 = summator[2]; var sum_3_level2 = sum_level2(3); //yields 21 var sum_4_level2 = sum_level2(4); //yields 55 var sum_5_level2 = sum_level2(5); //yields 120 Full Code Don’t think I was just going to hold off on the full file together and make you do the hard work…  Copy this into a new class file: public class Recursion<T> { private readonly Func<T, T> _functionToRecurse; public Recursion(Func<T, T> functionToRecurse) { if (functionToRecurse == null) { throw new ArgumentNullException("functionToRecurse", "The function to recurse can not be null"); } _functionToRecurse = functionToRecurse; } public Func<T,T> this[int level] { get { if (level < 1) { throw new ArgumentOutOfRangeException("level", level, "The level of recursion must be greater than 0"); } return this.GetXLevel(level); } } private Func<T, T> GetXLevel(int level) { if (level < 1) { throw new ArgumentOutOfRangeException("level", level, "The level of recursion must be greater than 0"); } if (level == 1) return _functionToRecurse; return _GetXLevel(level - 1, _functionToRecurse); } private Func<T, T> _GetXLevel(int level, Func<T, T> prevFunc) { if (level == 1) return y => prevFunc(_functionToRecurse(y)); return _GetXLevel(level - 1, y => prevFunc(_functionToRecurse(y))); } } Conclusion The great thing about this class, is that it can be used with any function with same input/output parameters.  I strived to find an implementation that I found clean and useful, and I finally settled on this.  If you have feedback – good or bad, I would love to hear it!

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