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  • Importance of a 1st Class Degree

    - by Nipuna Silva
    I'm currently at the 3rd year following a degree in Software Engineering. I'm thinking of moving into a research field in the future (programming language design, AI etc.) My problems are, What is the advantage/importance of carrying a 1st Class Degree (Honors for Americans) in to the industry rather than with just simple pass. Is it really important to have a 1st Class? Is it the practical knowledge i have to give priority or the theoretical knowledge, or both?

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  • Tag Cloud with jQuery Effect

    Tag Cloud WebControl built on the Star Field jQuery plug-in...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • XNA - Moving Background Calculations

    - by Jesse Emond
    Hi, My question is relatively hard to explain(for me, at least), so I'll go one step at a time and just tell me in the comments if it's not clear enough. So I'm making a "Defend Your Castle" type 2D game, where two players own a castle and create units that will move horizontally to try to destroy the opponent's base. Here's a screenshot of the game: The distance between both castles is much bigger in a real game though, bigger than the screen's width actually. Because the distance is bigger than the screen's width, I had to implement a simple 2D camera: Camera2D, which only holds a Location Vector2 (and I always make sure this camera is within the field area). Then, I just move all the game elements(castles, units, health bars) by that location, so that if a unit is at (5, 0), and the camera's location is (5, 0), then the unit's position will be moved by 5 units to the left, making it (0, 0) on the screen. At first, I simply used a static background with mountains and clouds(yeah, those are supposed to be mountains and clouds). Obviously, this looked awful: when you moved the camera, the background would stay immobile. Instead, I'd like to make a moving background, kind of a "scrolling" one. But rather than making a background with the same width as the distance between the castles, I'd like to make one that is a little bit smaller(but still bigger than the screen's width). I thought this would create an effect of "distance" with the background(but it might just look awful, too). Here's the background I'm testing with: I tried different ways, but none of them seems to work. I tried this: float backgroundFieldRatio = BackgroundTexture.Width / fieldWidth;//find the ratio between the background and the field. float backgroundPositionX = -cam.Location.X * backgroundFieldRatio;//move the background to the left When I run this with fieldWith = 1600, BackgroundTexture.Width = 1500 and while looking at the rightmost area, the background is offset to the left by a too big amount, and we can see the black clear color in the back, as you can see here: I hope I explained properly what I'm trying to achieve. Thank you for your time. Note: I didn't know what to look for on Google, so I thought I'd ask here.

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  • Hyper-V for Developers - presentation from NxtGenUG Oxford (including link to more info on Dynamic M

    - by Liam Westley
    Many thanks to Richard Hopton and the NxtGenUG guys in Oxford for inviting me to talk on Hyper-V for Developers last night, and for Research Machines for providing the venue.  It was great to have developers not yet using Hyper-V who were really interested in some of the finer points to help them with specific requirements. For those wanting to follow up on the topics I covered, you can download the presentation deck as either PDF (with speaker notes included) or as the original PowerPoint slidedeck,   http://www.tigernews.co.uk/blog-twickers/nxtgenugoxford/HyperV4Devs.pdf   http://www.tigernews.co.uk/blog-twickers/nxtgenugoxford/HyperV4Devs.zip I also mentioned the new feature, Dynamic Memory, coming in Service Pack 1, had been presented in a session at TechEd 2010 by Ben Armstrong, and you can download his presentation from here,   http://blogs.msdn.com/b/virtual_pc_guy/archive/2010/06/08/talking-about-dynamic-memory.aspx

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  • PostSharp, Obfuscation, and IL

    - by Simon Cooper
    Aspect-oriented programming (AOP) is a relatively new programming paradigm. Originating at Xerox PARC in 1994, the paradigm was first made available for general-purpose development as an extension to Java in 2001. From there, it has quickly been adapted for use in all the common languages used today. In the .NET world, one of the primary AOP toolkits is PostSharp. Attributes and AOP Normally, attributes in .NET are entirely a metadata construct. Apart from a few special attributes in the .NET framework, they have no effect whatsoever on how a class or method executes within the CLR. Only by using reflection at runtime can you access any attributes declared on a type or type member. PostSharp changes this. By declaring a custom attribute that derives from PostSharp.Aspects.Aspect, applying it to types and type members, and running the resulting assembly through the PostSharp postprocessor, you can essentially declare 'clever' attributes that change the behaviour of whatever the aspect has been applied to at runtime. A simple example of this is logging. By declaring a TraceAttribute that derives from OnMethodBoundaryAspect, you can automatically log when a method has been executed: public class TraceAttribute : PostSharp.Aspects.OnMethodBoundaryAspect { public override void OnEntry(MethodExecutionArgs args) { MethodBase method = args.Method; System.Diagnostics.Trace.WriteLine( String.Format( "Entering {0}.{1}.", method.DeclaringType.FullName, method.Name)); } public override void OnExit(MethodExecutionArgs args) { MethodBase method = args.Method; System.Diagnostics.Trace.WriteLine( String.Format( "Leaving {0}.{1}.", method.DeclaringType.FullName, method.Name)); } } [Trace] public void MethodToLog() { ... } Now, whenever MethodToLog is executed, the aspect will automatically log entry and exit, without having to add the logging code to MethodToLog itself. PostSharp Performance Now this does introduce a performance overhead - as you can see, the aspect allows access to the MethodBase of the method the aspect has been applied to. If you were limited to C#, you would be forced to retrieve each MethodBase instance using Type.GetMethod(), matching on the method name and signature. This is slow. Fortunately, PostSharp is not limited to C#. It can use any instruction available in IL. And in IL, you can do some very neat things. Ldtoken C# allows you to get the Type object corresponding to a specific type name using the typeof operator: Type t = typeof(Random); The C# compiler compiles this operator to the following IL: ldtoken [mscorlib]System.Random call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle( valuetype [mscorlib]System.RuntimeTypeHandle) The ldtoken instruction obtains a special handle to a type called a RuntimeTypeHandle, and from that, the Type object can be obtained using GetTypeFromHandle. These are both relatively fast operations - no string lookup is required, only direct assembly and CLR constructs are used. However, a little-known feature is that ldtoken is not just limited to types; it can also get information on methods and fields, encapsulated in a RuntimeMethodHandle or RuntimeFieldHandle: // get a MethodBase for String.EndsWith(string) ldtoken method instance bool [mscorlib]System.String::EndsWith(string) call class [mscorlib]System.Reflection.MethodBase [mscorlib]System.Reflection.MethodBase::GetMethodFromHandle( valuetype [mscorlib]System.RuntimeMethodHandle) // get a FieldInfo for the String.Empty field ldtoken field string [mscorlib]System.String::Empty call class [mscorlib]System.Reflection.FieldInfo [mscorlib]System.Reflection.FieldInfo::GetFieldFromHandle( valuetype [mscorlib]System.RuntimeFieldHandle) These usages of ldtoken aren't usable from C# or VB, and aren't likely to be added anytime soon (Eric Lippert's done a blog post on the possibility of adding infoof, methodof or fieldof operators to C#). However, PostSharp deals directly with IL, and so can use ldtoken to get MethodBase objects quickly and cheaply, without having to resort to string lookups. The kicker However, there are problems. Because ldtoken for methods or fields isn't accessible from C# or VB, it hasn't been as well-tested as ldtoken for types. This has resulted in various obscure bugs in most versions of the CLR when dealing with ldtoken and methods, and specifically, generic methods and methods of generic types. This means that PostSharp was behaving incorrectly, or just plain crashing, when aspects were applied to methods that were generic in some way. So, PostSharp has to work around this. Without using the metadata tokens directly, the only way to get the MethodBase of generic methods is to use reflection: Type.GetMethod(), passing in the method name as a string along with information on the signature. Now, this works fine. It's slower than using ldtoken directly, but it works, and this only has to be done for generic methods. Unfortunately, this poses problems when the assembly is obfuscated. PostSharp and Obfuscation When using ldtoken, obfuscators don't affect how PostSharp operates. Because the ldtoken instruction directly references the type, method or field within the assembly, it is unaffected if the name of the object is changed by an obfuscator. However, the indirect loading used for generic methods was breaking, because that uses the name of the method when the assembly is put through the PostSharp postprocessor to lookup the MethodBase at runtime. If the name then changes, PostSharp can't find it anymore, and the assembly breaks. So, PostSharp needs to know about any changes an obfuscator does to an assembly. The way PostSharp does this is by adding another layer of indirection. When PostSharp obfuscation support is enabled, it includes an extra 'name table' resource in the assembly, consisting of a series of method & type names. When PostSharp needs to lookup a method using reflection, instead of encoding the method name directly, it looks up the method name at a fixed offset inside that name table: MethodBase genericMethod = typeof(ContainingClass).GetMethod(GetNameAtIndex(22)); PostSharp.NameTable resource: ... 20: get_Prop1 21: set_Prop1 22: DoFoo 23: GetWibble When the assembly is later processed by an obfuscator, the obfuscator can replace all the method and type names within the name table with their new name. That way, the reflection lookups performed by PostSharp will now use the new names, and everything will work as expected: MethodBase genericMethod = typeof(#kGy).GetMethod(GetNameAtIndex(22)); PostSharp.NameTable resource: ... 20: #kkA 21: #zAb 22: #EF5a 23: #2tg As you can see, this requires direct support by an obfuscator in order to perform these rewrites. Dotfuscator supports it, and now, starting with SmartAssembly 6.6.4, SmartAssembly does too. So, a relatively simple solution to a tricky problem, with some CLR bugs thrown in for good measure. You don't see those every day!

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  • Suggestions for getting an open source electron beam tracking code going

    - by Boaz
    I work in the field of accelerator physics and synchrotron radiation. High energy electrons circulating in large rings of magnets produce x-rays that are used for a variety of different kinds of science. Running and improving these facilities requires controlling and modelling the electron beam as it circulates in the ring. A code to model this basically requires trackers to follow the electrons through the elements (something called a symplectic integrator), and then the computation of different parameters associated with this motion. The problem with these codes is that every facility has there own. In principle the code is not so complex. And as a modelling project, one might think it has some general interest. Who doesn't want to be able to create a track in space out of magnets and watch the electrons circulate? There is a Matlab based code to do this called Accelerator Toolbox, but the creator of the code is no longer in the field. I put the code in Sourceforge under the name atcollab. The basic resource is in C- it is the set of symplectic integrators. These are available in the atcollab code here. It has been useful to put the code on Sourceforge in order to exchange code, but the community of users is quite small and most are too busy to put that much time into collaboration. So in terms of really improving the code, I don't think it has been so successful. Any piece of this picture could be recreated without that much difficulty, but overall it is a bit complex, and because each lab has their own installation with lots of add-on Matlab code, people find it hard to really work together and share code. Somehow I think we need to involve a wider community in our development, or just use some standard tools. But for that, I suppose it needs to be of some general interest. I think symplectic integrators may have some general interest. And the part about a plug-in architecture to build up the ring ought to fit other patterns. Or the other option is to just accept that this is not a problem of general interest, and work harder within our small community. Suggestions, or anecdotes of analogous experience would be appreciated.

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  • Benefits of an Internet Marketing Course About SEO Article

    An online job is a great opportunity for the people to make money online and prosper in the environment of internet. It is not difficult to start earning online if you have basic knowledge of computer and internet. But taking some training in your field of work is always very helpful to grow your business. So is in the case of SEO article writing. This special technique is not so difficult but training can bring perfection in your articles.

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  • How To Protect Yourself From Bad Logo Services?

    The World Wide Web is so full of service providers in almost every field of business. However the recent boom in small businesses and home run businesses across the globe has also resulted in a boom ... [Author: Emily Matthew - Web Design and Development - May 20, 2010]

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  • Get Real Multitasking on Android With These 8 Floating Apps

    - by Chris Hoffman
    Android has decent multitasking, but the missing piece of the puzzle is the ability to have multiple apps on-screen at the same time – particularly useful on a larger tablet. Floating apps fill this need. Floating apps function as always-on-top windows, allowing you to watch videos, browse the web, take notes, or do other things while using another app. They demonstrate how Android’s interface is more flexible than iOS and the Modern UI in Windows. Secure Yourself by Using Two-Step Verification on These 16 Web Services How to Fix a Stuck Pixel on an LCD Monitor How to Factory Reset Your Android Phone or Tablet When It Won’t Boot

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  • Dark or light theme for Android apps?

    - by Philip Sheard
    My app allows the user to choose between a dark and a light theme, but which should it use as the default? It is a field sales app, a kind of glorified invoicing app for enterprise users. It is much larger than most apps in Google Play, and targets a vertical market. Originally I developed the app with a dark font, which was fairly standard at the time. That is still my personal preference, but most modern apps seem to have a light font.

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  • EBS Procurement - Approval Workflow

    - by Annemarie Provisero
    ADVISOR WEBCAST:  Approval Workflow PRODUCT FAMILY: EBS Procurement    February 15, 2011 at 14:00 UK Time, 9:00 am ET, 4:00 pm, Egypt Standard Time, 7:30 pm, India Time This one-hour session is recommended for technical and functional users who would like to know about APPROVAL WORKFLOW TROUBLESHOOTING. TOPICS WILL INCLUDE: Introduction Purchasing Approval Basics How to See the Workflow for a Purchasing Document Advanced Troubleshooting Helpful My Oracle Support Notes Conclusion A short, live demonstration (only if applicable) and question and answer period will be included. Oracle Advisor Webcasts are dedicated to building your awareness around our products and services. This session does not replace offerings from Oracle Global Support Services.  Click here to register for this session ------------------------------------------------------------------------------------------------------------- The above webcast is a service of the E-Business Suite Communities in My Oracle Support.For more information on other webcasts, please reference the Oracle Advisor Webcast Schedule.Click here to visit the E-Business Communities in My Oracle Support Note that all links require access to My Oracle Support.

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  • Is reference to bug/issue in commit message considered good practice?

    - by Christian P
    I'm working on a project where we have the source control set up to automatically write notes in the bug tracker. We simply write the bug issue ID in the commit message and the commit message is added as a note to the bug tracker. I can see only a few downsides for this practice. If sometime in the future the source code gets separated from the bug tracking software (or the reported bugs/issues are somehow lost). Or when someone is looking in the history of commits but doesn't have access to our bug tracker. My question is if having a bug/issue reference in the commit message is considered good practice? Are there some other downsides?

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  • Business Logo Design - Is Clients Input Important

    In today';s world, there is a cutthroat competition everywhere, so is in the field of logo designing. In a scenario like this, how you, as a logo design company would differentiate yourself in terms o... [Author: Gisselle Gloria - Web Design and Development - October 05, 2009]

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  • How to edit pdf metadata from command line?

    - by bdr529
    I need a command line tool for editing metadata of pdf-files. I'm using a Aiptek MyNote Premium tablet for writing my notes and minutes on this device, import them later and convert them to pdf automatically with a simple script using inkscape and ghostscript. Is there any command line tool to add some categories to the pdf's metadata, so i can find the pdf later (e.g. with gnome-do) by categories? Update: I tried the solution with pdftk and it works, but it seems that gnome-do doesn't take care of pdf-metadata. Is there a way to get gnome-do to do that?

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  • Theory Of A Weird Thought - Forms Submission

    - by user2738336
    In theory, if you were to open two computers that were perfectly synced together on a website that has a form. This form has fields where say for example the username has to be unique. Assuming both computers have the same information on the form, and in theory let's say that the submit button was pressed at the same time, and that these two computers have the exact same build and internet speed and the same response time from the server, whose information would be submitted to the database and whose information would be denied knowing the username field is unique.

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  • Java Spotlight Episode 100: JavaOne 2012 Part 1

    - by Roger Brinkley
    An interview with Arun Gupta on Glassfish, Geertjan Wielenga on Netbeans, and 15 year JavaOne alumin Robert Treacy on events and happenings at JavaOne 2012. Right-click or Control-click to download this MP3 file. You can also subscribe to the Java Spotlight Podcast Feed to get the latest podcast automatically. If you use iTunes you can open iTunes and subscribe with this link:  Java Spotlight Podcast in iTunes. Show Notes Events Sep 30-Oct 4, JavaONE, San Francisco Oct 3-4, Java Embedded @ JavaONE, San Francisco Oct 15-17, JAX London Oct 30-Nov 1, Arm TechCon, Santa Clara Oct 22-23, Freescale Technology Forum - Japan, Tokyo Oct 31, JFall, Netherlands Nov 2-3, JMagreb, Morocco Nov 13-17, Devoxx, Belgium Feature InterviewGlassFish Community Event will be conducted on Sep 30, 11am - 1pm. This is a fantastic opportunity for GlassFish users to meet and engage with the GlassFish Team in a casual setting.http://glassfish-event12.eventbrite.com/ Netbeans eventshttp://netbeans.dzone.com/news/meet-experts-java-ee-javafx http://netbeans.org/community/articles/javaone/2012/netbeans-day-2012.html http://netbeans.org/community/articles/javaone/2012/index.html

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  • How often do CPUs make calculation errors?

    - by veryfoolish
    In Dijkstra's Notes on Structured Programming he talks a lot about the provability of computer programs as abstract entities. As a corollary, he remarks how testing isn't enough. E.g., he points out the fact that it would be impossible to test a multiplication function f(x,y) = x*y for any large values of x and y across the entire ranges of x and y. My question concerns his misc. remarks on "lousy hardware". I know the essay was written in the 1970s when computer hardware was less reliable, but computers still aren't perfect, so they must make calculation mistakes sometimes. Does anybody know how often this happens or if there are any statistics on this?

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  • Cool Tools You Can Use: Validation Templates for PeopleSoft Contracts Processes

    - by Mark Rosenberg
    This is the first in a series of postings we’ll be making under the heading of Cool Tools You Can Use. Our PeopleSoft product management team identified the need for this series after reflecting on the many conversations we have each year with our PeopleSoft community members. During these conversations, we were discovering that customers and implementation partners were often not aware that solutions exist to the problems they were trying to address and that the solutions were readily available at no additional charge. Thus, the Cool Tools You Can Use series will describe the business challenge we’ve heard, the PeopleSoft solution to the challenge, and how you can learn more about the solution so that everyone can be sure to make full use of what PeopleSoft applications have to offer. The first cool tool we’ll look at is the Validation Template for PeopleSoft Contracts Process Requests, which was first released in December 2013 as part of PeopleSoft Contracts 9.2 Update Image 4. The business issue our customers highlighted to us is the need to tightly control but easily configure and manage the scope of data that any user can process when initiating a process. Control of each user’s span of impact is essential to reducing billing reconciliation issues, passing span of authority audits, and reducing (or even eliminating) the frequency of unexpected process results.  Setting Up the Validation Template for a PeopleSoft Contracts Process With the validation template, organizations can easily and quickly ensure the software restricts the scope of transactions a user can affect and gives organizations the confidence to know that business processes are being governed effectively. Additionally, this control of PeopleSoft Contracts process requests can be applied and easily maintained and adjusted from a web browser thereby enabling analysts to administer the rules without having to engage software developers to customize the software. During the field validation template setup, an analyst specifies the combinations of fields that must contain values when a user tries to setup a run control and initiate a PeopleSoft Contracts process from a process request page. For example, for the Process Limits component, an organization could require that users enter a valid combination of values for the business unit, contract, and contract type fields or a value in the contract administrator field. Until the user enters a valid combination of entries on the process request page, he cannot launch the process. With the validation template activated for process request pages, organizations can be confident that PeopleSoft Contracts users will not accidentally begin generating invoices or triggering other revenue management processes for transactions beyond their scope of authority. To learn more about the Validation Template, please review the Defining Validation Templates section of the PeopleSoft Contracts PeopleBooks. 

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  • SQL Server 2008 R2 Reporting Services: A generic error occurred in GDI+

    - by Greg Low
    While building some maps today in SQL Server 2008 R2 Reporting Services, I kept coming up with an error that said: A generic error occurred in GDI+ I was struggling to think what I'd done wrong. After much nashing of teeth and removal of hair, I finally worked out what the error was. When I got to the "Choose Color Scheme and Visualization" page of the map wizard for building a color analytical map, I hadn't picked the correct value for the "Field to Visualize" drop-down. I'm guessing that because...(read more)

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  • The Unintended Consequences of Sound Security Policy

    - by Tanu Sood
    v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);} Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Calibri","sans-serif"; mso-bidi-font-family:"Times New Roman";} Author: Kevin Moulton, CISSP, CISM Meet the Author: Kevin Moulton, Senior Sales Consulting Manager, Oracle Kevin Moulton, CISSP, CISM, has been in the security space for more than 25 years, and with Oracle for 7 years. He manages the East Enterprise Security Sales Consulting Team. He is also a Distinguished Toastmaster. Follow Kevin on Twitter at twitter.com/kevin_moulton, where he sometimes tweets about security, but might also tweet about running, beer, food, baseball, football, good books, or whatever else grabs his attention. Kevin will be a regular contributor to this blog so stay tuned for more posts from him. When I speak to a room of IT administrators, I like to begin by asking them if they have implemented a complex password policy. Generally, they all nod their heads enthusiastically. I ask them if that password policy requires long passwords. More nodding. I ask if that policy requires upper and lower case letters – faster nodding – numbers – even faster – special characters – enthusiastic nodding all around! I then ask them if their policy also includes a requirement for users to regularly change their passwords. Now we have smiles with the nodding! I ask them if the users have different IDs and passwords on the many systems that they have access to. Of course! I then ask them if, when they walk around the building, they see something like this: Thanks to Jake Ludington for the nice example. Can these administrators be faulted for their policies? Probably not but, in the end, end-users will find a way to get their job done efficiently. Post-It Notes to the rescue! I was visiting a business in New York City one day which was a perfect example of this problem. First I walked up to the security desk and told them where I was headed. They asked me if they should call upstairs to have someone escort me. Is that my call? Is that policy? I said that I knew where I was going, so they let me go. Having the conference room number handy, I wandered around the place in a search of my destination. As I walked around, unescorted, I noticed the post-it note problem in abundance. Had I been so inclined, I could have logged in on almost any machine and into any number of systems. When I reached my intended conference room, I mentioned my post-it note observation to the two gentlemen with whom I was meeting. One of them said, “You mean like this,” and he produced a post it note full of login IDs and passwords from his breast pocket! I gave him kudos for not hanging the list on his monitor. We then talked for the rest of the meeting about the difficulties faced by the employees due to the security policies. These policies, although well-intended, made life very difficult for the end-users. Most users had access to 8 to 12 systems, and the passwords for each expired at a different times. The post-it note solution was understandable. Who could remember even half of them? What could this customer have done differently? I am a fan of using a provisioning system, such as Oracle Identity Manager, to manage all of the target systems. With OIM, and email could be automatically sent to all users when it was time to change their password. The end-users would follow a link to change their password on a web page, and then OIM would propagate that password out to all of the systems that the user had access to, even if the login IDs were different. Another option would be an Enterprise Single-Sign On Solution. With Oracle eSSO, all of a user’s credentials would be stored in a central, encrypted credential store. The end-user would only have to login to their machine each morning and then, as they moved to each new system, Oracle eSSO would supply the credentials. Good-bye post-it notes! 3M may be disappointed, but your end users will thank you. I hear people say that this post-it note problem is not a big deal, because the only people who would see the passwords are fellow employees. Do you really know who is walking around your building? What are the password policies in your business? How do the end-users respond?

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  • PostSharp, Obfuscation, and IL

    - by simonc
    Aspect-oriented programming (AOP) is a relatively new programming paradigm. Originating at Xerox PARC in 1994, the paradigm was first made available for general-purpose development as an extension to Java in 2001. From there, it has quickly been adapted for use in all the common languages used today. In the .NET world, one of the primary AOP toolkits is PostSharp. Attributes and AOP Normally, attributes in .NET are entirely a metadata construct. Apart from a few special attributes in the .NET framework, they have no effect whatsoever on how a class or method executes within the CLR. Only by using reflection at runtime can you access any attributes declared on a type or type member. PostSharp changes this. By declaring a custom attribute that derives from PostSharp.Aspects.Aspect, applying it to types and type members, and running the resulting assembly through the PostSharp postprocessor, you can essentially declare 'clever' attributes that change the behaviour of whatever the aspect has been applied to at runtime. A simple example of this is logging. By declaring a TraceAttribute that derives from OnMethodBoundaryAspect, you can automatically log when a method has been executed: public class TraceAttribute : PostSharp.Aspects.OnMethodBoundaryAspect { public override void OnEntry(MethodExecutionArgs args) { MethodBase method = args.Method; System.Diagnostics.Trace.WriteLine( String.Format( "Entering {0}.{1}.", method.DeclaringType.FullName, method.Name)); } public override void OnExit(MethodExecutionArgs args) { MethodBase method = args.Method; System.Diagnostics.Trace.WriteLine( String.Format( "Leaving {0}.{1}.", method.DeclaringType.FullName, method.Name)); } } [Trace] public void MethodToLog() { ... } Now, whenever MethodToLog is executed, the aspect will automatically log entry and exit, without having to add the logging code to MethodToLog itself. PostSharp Performance Now this does introduce a performance overhead - as you can see, the aspect allows access to the MethodBase of the method the aspect has been applied to. If you were limited to C#, you would be forced to retrieve each MethodBase instance using Type.GetMethod(), matching on the method name and signature. This is slow. Fortunately, PostSharp is not limited to C#. It can use any instruction available in IL. And in IL, you can do some very neat things. Ldtoken C# allows you to get the Type object corresponding to a specific type name using the typeof operator: Type t = typeof(Random); The C# compiler compiles this operator to the following IL: ldtoken [mscorlib]System.Random call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle( valuetype [mscorlib]System.RuntimeTypeHandle) The ldtoken instruction obtains a special handle to a type called a RuntimeTypeHandle, and from that, the Type object can be obtained using GetTypeFromHandle. These are both relatively fast operations - no string lookup is required, only direct assembly and CLR constructs are used. However, a little-known feature is that ldtoken is not just limited to types; it can also get information on methods and fields, encapsulated in a RuntimeMethodHandle or RuntimeFieldHandle: // get a MethodBase for String.EndsWith(string) ldtoken method instance bool [mscorlib]System.String::EndsWith(string) call class [mscorlib]System.Reflection.MethodBase [mscorlib]System.Reflection.MethodBase::GetMethodFromHandle( valuetype [mscorlib]System.RuntimeMethodHandle) // get a FieldInfo for the String.Empty field ldtoken field string [mscorlib]System.String::Empty call class [mscorlib]System.Reflection.FieldInfo [mscorlib]System.Reflection.FieldInfo::GetFieldFromHandle( valuetype [mscorlib]System.RuntimeFieldHandle) These usages of ldtoken aren't usable from C# or VB, and aren't likely to be added anytime soon (Eric Lippert's done a blog post on the possibility of adding infoof, methodof or fieldof operators to C#). However, PostSharp deals directly with IL, and so can use ldtoken to get MethodBase objects quickly and cheaply, without having to resort to string lookups. The kicker However, there are problems. Because ldtoken for methods or fields isn't accessible from C# or VB, it hasn't been as well-tested as ldtoken for types. This has resulted in various obscure bugs in most versions of the CLR when dealing with ldtoken and methods, and specifically, generic methods and methods of generic types. This means that PostSharp was behaving incorrectly, or just plain crashing, when aspects were applied to methods that were generic in some way. So, PostSharp has to work around this. Without using the metadata tokens directly, the only way to get the MethodBase of generic methods is to use reflection: Type.GetMethod(), passing in the method name as a string along with information on the signature. Now, this works fine. It's slower than using ldtoken directly, but it works, and this only has to be done for generic methods. Unfortunately, this poses problems when the assembly is obfuscated. PostSharp and Obfuscation When using ldtoken, obfuscators don't affect how PostSharp operates. Because the ldtoken instruction directly references the type, method or field within the assembly, it is unaffected if the name of the object is changed by an obfuscator. However, the indirect loading used for generic methods was breaking, because that uses the name of the method when the assembly is put through the PostSharp postprocessor to lookup the MethodBase at runtime. If the name then changes, PostSharp can't find it anymore, and the assembly breaks. So, PostSharp needs to know about any changes an obfuscator does to an assembly. The way PostSharp does this is by adding another layer of indirection. When PostSharp obfuscation support is enabled, it includes an extra 'name table' resource in the assembly, consisting of a series of method & type names. When PostSharp needs to lookup a method using reflection, instead of encoding the method name directly, it looks up the method name at a fixed offset inside that name table: MethodBase genericMethod = typeof(ContainingClass).GetMethod(GetNameAtIndex(22)); PostSharp.NameTable resource: ... 20: get_Prop1 21: set_Prop1 22: DoFoo 23: GetWibble When the assembly is later processed by an obfuscator, the obfuscator can replace all the method and type names within the name table with their new name. That way, the reflection lookups performed by PostSharp will now use the new names, and everything will work as expected: MethodBase genericMethod = typeof(#kGy).GetMethod(GetNameAtIndex(22)); PostSharp.NameTable resource: ... 20: #kkA 21: #zAb 22: #EF5a 23: #2tg As you can see, this requires direct support by an obfuscator in order to perform these rewrites. Dotfuscator supports it, and now, starting with SmartAssembly 6.6.4, SmartAssembly does too. So, a relatively simple solution to a tricky problem, with some CLR bugs thrown in for good measure. You don't see those every day! Cross posted from Simple Talk.

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  • We've completed the first iteration

    - by CliveT
    There are a lot of features in C# that are implemented by the compiler and not by the underlying platform. One such feature is a lambda expression. Since local variables cannot be accessed once the current method activation finishes, the compiler has to go out of its way to generate a new class which acts as a home for any variable whose lifetime needs to be extended past the activation of the procedure. Take the following example:     Random generator = new Random();     Func func = () = generator.Next(10); In this case, the compiler generates a new class called c_DisplayClass1 which is marked with the CompilerGenerated attribute. [CompilerGenerated] private sealed class c__DisplayClass1 {     // Fields     public Random generator;     // Methods     public int b__0()     {         return this.generator.Next(10);     } } Two quick comments on this: (i)    A display was the means that compilers for languages like Algol recorded the various lexical contours of the nested procedure activations on the stack. I imagine that this is what has led to the name. (ii)    It is a shame that the same attribute is used to mark all compiler generated classes as it makes it hard to figure out what they are being used for. Indeed, you could imagine optimisations that the runtime could perform if it knew that classes corresponded to certain high level concepts. We can see that the local variable generator has been turned into a field in the class, and the body of the lambda expression has been turned into a method of the new class. The code that builds the Func object simply constructs an instance of this class and initialises the fields to their initial values.     c__DisplayClass1 class2 = new c__DisplayClass1();     class2.generator = new Random();     Func func = new Func(class2.b__0); Reflector already contains code to spot this pattern of code and reproduce the form containing the lambda expression, so this is example is correctly decompiled. The use of compiler generated code is even more spectacular in the case of iterators. C# introduced the idea of a method that could automatically store its state between calls, so that it can pick up where it left off. The code can express the logical flow with yield return and yield break denoting places where the method should return a particular value and be prepared to resume.         {             yield return 1;             yield return 2;             yield return 3;         } Of course, there was already a .NET pattern for expressing the idea of returning a sequence of values with the computation proceeding lazily (in the sense that the work for the next value is executed on demand). This is expressed by the IEnumerable interface with its Current property for fetching the current value and the MoveNext method for forcing the computation of the next value. The sequence is terminated when this method returns false. The C# compiler links these two ideas together so that an IEnumerator returning method using the yield keyword causes the compiler to produce the implementation of an Iterator. Take the following piece of code.         IEnumerable GetItems()         {             yield return 1;             yield return 2;             yield return 3;         } The compiler implements this by defining a new class that implements a state machine. This has an integer state that records which yield point we should go to if we are resumed. It also has a field that records the Current value of the enumerator and a field for recording the thread. This latter value is used for optimising the creation of iterator instances. [CompilerGenerated] private sealed class d__0 : IEnumerable, IEnumerable, IEnumerator, IEnumerator, IDisposable {     // Fields     private int 1__state;     private int 2__current;     public Program 4__this;     private int l__initialThreadId; The body gets converted into the code to construct and initialize this new class. private IEnumerable GetItems() {     d__0 d__ = new d__0(-2);     d__.4__this = this;     return d__; } When the class is constructed we set the state, which was passed through as -2 and the current thread. public d__0(int 1__state) {     this.1__state = 1__state;     this.l__initialThreadId = Thread.CurrentThread.ManagedThreadId; } The state needs to be set to 0 to represent a valid enumerator and this is done in the GetEnumerator method which optimises for the usual case where the returned enumerator is only used once. IEnumerator IEnumerable.GetEnumerator() {     if ((Thread.CurrentThread.ManagedThreadId == this.l__initialThreadId)               && (this.1__state == -2))     {         this.1__state = 0;         return this;     } The state machine itself is implemented inside the MoveNext method. private bool MoveNext() {     switch (this.1__state)     {         case 0:             this.1__state = -1;             this.2__current = 1;             this.1__state = 1;             return true;         case 1:             this.1__state = -1;             this.2__current = 2;             this.1__state = 2;             return true;         case 2:             this.1__state = -1;             this.2__current = 3;             this.1__state = 3;             return true;         case 3:             this.1__state = -1;             break;     }     return false; } At each stage, the current value of the state is used to determine how far we got, and then we generate the next value which we return after recording the next state. Finally we return false from the MoveNext to signify the end of the sequence. Of course, that example was really simple. The original method body didn't have any local variables. Any local variables need to live between the calls to MoveNext and so they need to be transformed into fields in much the same way that we did in the case of the lambda expression. More complicated MoveNext methods are required to deal with resources that need to be disposed when the iterator finishes, and sometimes the compiler uses a temporary variable to hold the return value. Why all of this explanation? We've implemented the de-compilation of iterators in the current EAP version of Reflector (7). This contrasts with previous version where all you could do was look at the MoveNext method and try to figure out the control flow. There's a fair amount of things we have to do. We have to spot the use of a CompilerGenerated class which implements the Enumerator pattern. We need to go to the class and figure out the fields corresponding to the local variables. We then need to go to the MoveNext method and try to break it into the various possible states and spot the state transitions. We can then take these pieces and put them back together into an object model that uses yield return to show the transition points. After that Reflector can carry on optimising using its usual optimisations. The pattern matching is currently a little too sensitive to changes in the code generation, and we only do a limited analysis of the MoveNext method to determine use of the compiler generated fields. In some ways, it is a pity that iterators are compiled away and there is no metadata that reflects the original intent. Without it, we are always going to dependent on our knowledge of the compiler's implementation. For example, we have noticed that the Async CTP changes the way that iterators are code generated, so we'll have to do some more work to support that. However, with that warning in place, we seem to do a reasonable job of decompiling the iterators that are built into the framework. Hopefully, the EAP will give us a chance to find examples where we don't spot the pattern correctly or regenerate the wrong code, and we can improve things. Please give it a go, and report any problems.

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  • Getting user generated content with no titles to rank

    - by hugo
    We are creating a site that allows users to generate content. The user is provided with a text field only (no title), similar to Twitter, Facebook, and Google+. Each piece of content created by the users will have a dedicated page/URL. Since the page has no title, I was wondering how search engines will index and display our pages. If the content was shared on other social networks, what will those results look like if there is no title for the open graph or Twitter tags?

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  • E-commerce for custom orders/customer image upload

    - by ansarob
    We have a client that needs an e-commerce site set up pretty quickly. As I have no experience with e-commerce, I am looking for some guidance. Basically, the two big features we need are: Ability for customer to add info about order (example: the name the customer wants to be put on the customizable product they ordered) Ability for customer to upload photo of product to be customized I hope this makes sense. Right now I am really looking into Shopify, but I can't tell if it does everything we need. I know you can add order notes when checking out, but not sure about image upload (maybe it can be added as an app through the API?).

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  • Working for international NGO's as a programmer

    - by Keyslinger
    I have begun a career as a web application and database developer while slowly discovering the passion I have for work in the international development sector. Since this is not the most obvious line of work for someone with my credentials, it seems to me that special care must be taken in order to court international non-governmental organisations (NGOs) and position myself in the field. Aside from adding grant-writing to my skill set and getting volunteer experience, what indispensable advice do you have for a fledgling programmer who wants to save the world?

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