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  • BizTalk 2009 - SQL Server Job Configuration

    - by StuartBrierley
    Following the installation of Biztalk Server 2009 on my development laptop I used the BizTalk Server Best Practice Analyser which highlighted the fact that two of the SQL Server Agent jobs that BizTalk relies on were not running successfully.  Upon investigation it turned out that these jobs needed to be configured before they would run successfully. To configure these jobs open SQL Server Management Studio, expand SQL Server Agent > Jobs and double click on the appropriate job.  Select Steps and then edit the appropriate entries. Backup BizTalk Server (BizTalkMgmtDb) This job is comprised of three steps BackupFull, MarkAndBackupLog and ClearBackupHistory. BackupFull exec [dbo].[sp_BackupAllFull_Schedule] ‘d’ /* Frequency */,‘BTS’ /* Name */,‘<destination path>’ /* location of backup files */ The frequency here is set/left as daily The name is left as BTS You must provide a full destination path for the backup files to be stored. There are also two optional parameters: A flag that controls if the job forces a full backup if a partial backup fails A parameter to control the time of day to run the full backup; the default is midnight UTC time For example: exec [dbo].[sp_BackupAllFull_Schedule] ‘d’ /* Frequency */,‘BTS’ /* Name */,‘<destination path>’ /* location of backup files */ , 0, 22 MarkAndBackUpLog exec [dbo].[sp_MarkAll] ‘BTS’ /* Log mark name */,’<destination path>’  /*location of backup files */ You must provide a destination path for the log backups. Optionally you can also add an extra parameter that tells the procedure to use local time: exec [dbo].[sp_MarkAll] ‘BTS’ /* Log mark name */,’<destination path>’  /*location of backup files */ ,1 Clear Backup History exec [dbo].[sp_DeleteBackupHistory] @DaysToKeep=7 This will clear out the instances in the MarkLog table older than 7 days.    DTA Purge and Archive (BizTalkDTADb) This job is comprised of a single step. Archive and Purge exec dtasp_BackupAndPurgeTrackingDatabase 0, --@nLiveHours tinyint, 1, --@nLiveDays tinyint = 0, 30, --@nHardDeleteDays tinyint = 0, null, --@nvcFolder nvarchar(1024) = null, null, --@nvcValidatingServer sysname = null, 0 --@fForceBackup int = 0 Any completed instance that is older than the live days plus live hours will be deleted, as will any associated data. Any data older than the HardDeleteDays will be deleted - this means that those long running orchestration instances that would otherwise never be purged will at some point have their data cleared down while allowing the instance to continue, thus preventing the DTA databse from growing indefinitely.  This should always be greater than the soft purge window. The NVC folder is the path for the backup files, if this is null the job will not run failing with the error : DTA Purge and Archive (BizTalkDTADb) Job failed SQL Server Management Studio, job activity monitor, view history The @nvcFolder parameter cannot be null. Archive and Purge step How long you choose to keep instances in the Tracking Database is really up to you. For development I have set this up as: exec dtasp_BackupAndPurgeTrackingDatabase 0, 1, 30, ’<destination path>’, null, 0 On a live server you may want to adjust these figures: exec dtasp_BackupAndPurgeTrackingDatabase 0, 15, 20, ’<destination path>’, null, 0

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  • Can I uninstall and reinstall Ubuntu Software Center?

    - by schonjones
    Since migrating to a true install and upgrading to 12.04 I have had several problems that seem to relate to the Ubuntu Software Center. Hanging at applying changes and blank screen on screen lock only when it is running, for instance. My question is: Can I safely uninstall and reinstall Ubuntu Software Center and could this possibly fix those problems or are they just bugs I have to wait for updates for?

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  • Solution for developers wanting to run a standalone WLS 10.3.6 server against JDev 11.1.1.6.0

    - by Chris Muir
    In my previous post I discussed how to install the 11.1.1.6.0 ADF Runtimes into a standalone WLS 10.3.6 server by using the ADF Runtime installer, not the JDeveloper installer.  Yet there's still a problem for developers here because JDeveloper 11.1.1.6.0 comes coupled with a WLS 10.3.5 server.  What if you want to develop, deploy and test with a 10.3.6 server?  Have we lost the ability to integrate the IDE and the WLS server where we can run and stop the server, deploy our apps automatically the server and more? JDeveloper actually solved this issue sometime back but not many people will have recognized the feature for what it does as it wasn't needed until now. Via the Application Server Navigator you can create 2 types of connections, one to a remote "standalone WLS" and another to an "integrated WLS".  It's this second option that is useful because what we can do is install a local standalone WLS 10.3.6 server on our developer PC, then create a separate "integrated WLS" connection to the standalone server.  Then by accessing your Application's properties through the Application menu -> Application Properties -> Run -> Bind to Integration Application Server option we can choose the newly created WLS server connection to work with our application. In this way JDeveloper will now treat the new server as if it was the integrated WLS.  It will start when we run and deploy our applications, terminate it at request and so on.  Of course don't forget you still need to install the ADF Runtimes for the server to be able to work with ADF applications. Note there is bug 13917844 lurking in the Application Server Navigator for at least JDev 11.1.1.6.0 and earlier.  If you right click the new connection and select "Start Server Instance" it will often start one of the other existing connections instead (typically the original IntegratedWebLogicServer connection).  If you want to manually start the server you can bypass this by using the Run menu -> Start Server Instance option which works correctly.

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  • Subterranean IL: Volatile

    - by Simon Cooper
    This time, we'll be having a look at the volatile. prefix instruction, and one of the differences between volatile in IL and C#. The volatile. prefix volatile is a tricky one, as there's varying levels of documentation on it. From what I can see, it has two effects: It prevents caching of the load or store value; rather than reading or writing to a cached version of the memory location (say, the processor register or cache), it forces the value to be loaded or stored at the 'actual' memory location, so it is then immediately visible to other threads. It forces a memory barrier at the prefixed instruction. This ensures instructions don't get re-ordered around the volatile instruction. This is slightly more complicated than it first seems, and only seems to matter on certain architectures. For more details, Joe Duffy has a blog post going into the details. For this post, I'll be concentrating on the first aspect of volatile. Caching field accesses To demonstrate this, I created a simple multithreaded IL program. It boils down to the following code: .class public Holder { .field public static class Holder holder .field public bool stop .method public static specialname void .cctor() { newobj instance void Holder::.ctor() stsfld class Holder Holder::holder ret }}.method private static void Main() { .entrypoint // Thread t = new Thread(new ThreadStart(DoWork)) // t.Start() // Thread.Sleep(2000) // Console.WriteLine("Stopping thread...") ldsfld class Holder Holder::holder ldc.i4.1 stfld bool Holder::stop call instance void [mscorlib]System.Threading.Thread::Join() ret}.method private static void DoWork() { ldsfld class Holder Holder::holder // while (!Holder.holder.stop) {} DoWork: dup ldfld bool Holder::stop brfalse DoWork pop ret} If you compile and run this code, you'll find that the call to Thread.Join() never returns - the DoWork spinlock is reading a cached version of Holder.stop, which is never being updated with the new value set by the Main method. Adding volatile to the ldfld fixes this: dupvolatile.ldfld bool Holder::stopbrfalse DoWork The volatile ldfld forces the field access to read direct from heap memory, which is then updated by the main thread, rather than using a cached copy. volatile in C# This highlights one of the differences between IL and C#. In IL, volatile only applies to the prefixed instruction, whereas in C#, volatile is specified on a field to indicate that all accesses to that field should be volatile (interestingly, there's no mention of the 'no caching' aspect of volatile in the C# spec; it only focuses on the memory barrier aspect). Furthermore, this information needs to be stored within the assembly somehow, as such a field might be accessed directly from outside the assembly, but there's no concept of a 'volatile field' in IL! How this information is stored with the field will be the subject of my next post.

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  • What precautions should I take when moving a hard drive from one computer to another?

    - by Colin Dean
    I'm planning to move a hard drive from one server machine to another. The hard drive is an IDE drive. The motherboards are different, as are the memory and such. In this instance, graphics isn't a problem because this is just Ubuntu Server. Are there any precautions I should take, or steps I can do beforehand, in order to make this go as smoothly as possible? I've of course already backed up /home directories and configurations in /etc and /var.

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  • Is there or why not having a ruby technology specification similar to Java's JSR?

    - by romeu.hcf
    I think on a community portal where specifications are made, documented and specified to reference libraries and systems implementation. An example: A specification for Message Queue where redis clients, for instance, could implement it and where the libraries could be validated by the specification's test suite. Redic, redis-rb, hiredis, redis-connection-pool, redis-namespace should all implement this specification. This way, being easily replaced.

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  • BizTalk Send Ports, Delivery Notification and ACK / NACK messages

    - by Robert Kokuti
    Recently I worked on an orchestration which sent messages out to a Send Port on a 'fire and forget' basis. The idea was that once the orchestration passed the message to the Messagebox, it was left to BizTalk to manage the sending process. Should the send operation fail, the Send Port got suspended, and the orchestration completed asynchronously, regardless of the Send Port success or failure. However, we still wanted to log the sending success, using the ACK / NACK messages. On normal ports, BizTalk generates ACK / NACK messages back to the Messagebox, if the logical port's Delivery Notification property is set to 'Transmitted'. Unfortunately, this setting also causes the orchestration to wait for the send port's result, and should the Send Port fail, the orchestration will also receive a 'DeliveryFailureException' exception. So we may end up with a suspended port and a suspended orchestration - not the outcome wanted here, there was no value in suspending the orchestration in our case. There are a couple of ways to fix this: 1. Catch the DeliveryFailureException  (full type name Microsoft.XLANGs.BaseTypes.DeliveryFailureException) and do nothing in the orchestration's exception block. Although this works, it still slows down the orchestration as the orchestration still has to wait for the outcome of the send port operation. 2. Use a Direct Port instead, and set the ACK request on the message Context, prior passing to the port: msgToSend(BTS.AckRequired) = true; This has to be done in an expression shape, as a Direct logical port does not have Delivery Notification property - make sure to add a reference to Microsoft.BizTalk.GlobalPropertySchemas. Setting this context value in the message will cause the messaging agent to create an appropriate ACK or NACK message after the port execution. The ACK / NACK messages can be caught and logged by dedicated Send Ports, filtering on BTS.AckType value (which is either ACK or NACK). ACK/NACK messages are treated in a special way by BizTalk, and a useful feature is that the original message's context values are copied to the ACK/NACK message context - these can be used for logging the right information. Other useful context properties of the ACK/NACK messages: -  BTS.AckSendPortName can be used to identify the original send port. - BTS.AckOwnerID, aka http://schemas.microsoft.com/BizTalk/2003/system-properties.AckOwnerID - holds the instance ID of the failed Send Port - can be used to resubmit / terminate the instance Someone may ask, can we just turn off the Delivery Notification on a 'normal' port, and set the AckRequired property on the message as for a Direct port. Unfortunately, this does not work - BizTalk seems to remove this property automatically, if the message goes through a port where Delivery Notification is set to None.

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  • How to use Chrome to access Oracle Applications

    - by Pan.Tian
    So far,Chrome browser is still not certified by Oracle Application, so you can not access Oracle Apps via Chrome.But you can install a chrome Extension to access Oracle Application(It works fine for 11i or R12 instance) Chrome Plugin:Oracle EBS R12 Enablement for Chrome You can use this Chrome Extension to log in Oracle E-Business R12 Form UI without FRM-92129(or FRM-92120) error which say the file Registry.dat lost. Plugin Author: zorrofox (see:http://www.itpub.net/forum.php?mod=viewthread&tid=1724526&page=1#pid20409128)

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  • How do I manually install the package selections presented in tasksel?

    - by joe
    If you forgot to select some software at the "Software Selection" screen on a fresh install, what are the commands to install them after the fact. I know you can install them manually at anytime after everything is said and done, but what are the commands to install just as if you [*]starred them on that screen. For instance: sudo apt-get install lamp-server^ will install the LAMP Server. What are the commands for the DNS Server, Mail Server and Tomcat Java server?

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  • More info: a "stand-alone" installer for Management Studio Express 2008

    - by AaronBertrand
    Last February, I blogged about something I was initially very happy about: a stand-alone installer for Management Studio Express (SSMSE) 2008 . Now users could allegedly download a much smaller installer, and only install the client tools without having to install an instance of SQL Server Express. While the latter is true, the former remains a pipe dream. Bill Ramos stated in his 2009-02-20 announcement : "We teased out the Tools portion of SQL Server 2008 Express with Tools into it’s own download."...(read more)

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  • Ways to serve AWS from another domain

    - by mplungjan
    I have installed Ghost on AWS (it is running node) I very much dislike the URL they gave me http://ec2-nn-nnn-nnn-nnn.us-west-2.compute.amazonaws.com/ghost/ I own a domain and linux hosting (but not a VPS) - what would be a practical way to serve my blog via URLS on my own (sub) domain? I can use php and access .htaccess on my domain - possibly do things on the ASW instance too (let me know what to look for)

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  • Restoring MSDB

    - by David-Betteridge
    We recently performed a disaster recovery exercise which included the restoration of the MSDB database onto our DR server.  I did a quick google to see if there were any special considerations and found the following MS article.  Considerations for Restoring the model and msdb Databases (http://msdn.microsoft.com/en-us/library/ms190749(v=sql.105).aspx).   It said both the original and replacement servers must be on the same version,  I double-checked and in my case they are both SQL Server 2008 R2 SP1 (10.50.2500).. So I went ahead and stopped SQL Server agent, restored the database and restarted the agent.  Checked the jobs and they were all there, everything looked great, and was until the server was rebooted a few days later.Then the syspolicy_purge_history job started failing on the 3rd step with the error message “Unable to start execution of step 3 (reason: The PowerShell subsystem failed to load [see the SQLAGENT.OUT file for details]; The job has been suspended). The step failed.”   A bit more googling pointed me to the msdb.dbo.syssubsystems table SELECT * FROM msdb.dbo.syssubsystems WHERE start_entry_point ='PowerShellStart'   And in particular the value for the subsystem_dll. It still had the path to the SQLPOWERSHELLSS.DLL but on the old server. The DR instance has a different name to the live instance and so the paths are different.   This was quickly fixed with the following SQL Use msdb; GO sp_configure 'allow updates', 1 ; RECONFIGURE WITH OVERRIDE ; GO UPDATE msdb.dbo.syssubsystems SET subsystem_dll='C:\Program Files\Microsoft SQL Server\MSSQL10_50.DR\MSSQL\binn\SQLPOWERSHELLSS.DLL' WHERE start_entry_point ='PowerShellStart'; GO sp_configure 'allow updates', 0; RECONFIGURE WITH OVERRIDE ; GO Stopped and started SQL Server agent and now the job completes.   I then wondered if anything else might be broken, SELECT subsystem_dll FROM msdb.dbo.syssubsystems Shows a further 10 wrong paths – fortunately for parts of SQL (replication, SSIS etc) we aren’t using! Lessons Learnt 1.       DR exercises are a good thing! 2.       Keep the Live and DR environments as similar as possible.    

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  • Subterranean IL: Exception handling 1

    - by Simon Cooper
    Today, I'll be starting a look at the Structured Exception Handling mechanism within the CLR. Exception handling is quite a complicated business, and, as a result, the rules governing exception handling clauses in IL are quite strict; you need to be careful when writing exception clauses in IL. Exception handlers Exception handlers are specified using a .try clause within a method definition. .try <TryStartLabel> to <TryEndLabel> <HandlerType> handler <HandlerStartLabel> to <HandlerEndLabel> As an example, a basic try/catch block would be specified like so: TryBlockStart: // ... leave.s CatchBlockEndTryBlockEnd:CatchBlockStart: // at the start of a catch block, the exception thrown is on the stack callvirt instance string [mscorlib]System.Object::ToString() call void [mscorlib]System.Console::WriteLine(string) leave.s CatchBlockEnd CatchBlockEnd: // method code continues... .try TryBlockStart to TryBlockEnd catch [mscorlib]System.Exception handler CatchBlockStart to CatchBlockEnd There are four different types of handler that can be specified: catch <TypeToken> This is the standard exception catch clause; you specify the object type that you want to catch (for example, [mscorlib]System.ArgumentException). Any object can be thrown as an exception, although Microsoft recommend that only classes derived from System.Exception are thrown as exceptions. filter <FilterLabel> A filter block allows you to provide custom logic to determine if a handler block should be run. This functionality is exposed in VB, but not in C#. finally A finally block executes when the try block exits, regardless of whether an exception was thrown or not. fault This is similar to a finally block, but a fault block executes only if an exception was thrown. This is not exposed in VB or C#. You can specify multiple catch or filter handling blocks in each .try, but fault and finally handlers must have their own .try clause. We'll look into why this is in later posts. Scoped exception handlers The .try syntax is quite tricky to use; it requires multiple labels, and you've got to be careful to keep separate the different exception handling sections. However, starting from .NET 2, IL allows you to use scope blocks to specify exception handlers instead. Using this syntax, the example above can be written like so: .try { // ... leave.s EndSEH}catch [mscorlib]System.Exception { callvirt instance string [mscorlib]System.Object::ToString() call void [mscorlib]System.Console::WriteLine(string) leave.s EndSEH}EndSEH:// method code continues... As you can see, this is much easier to write (and read!) than a stand-alone .try clause. Next time, I'll be looking at some of the restrictions imposed by SEH on control flow, and how the C# compiler generated exception handling clauses.

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  • Find your HEAPS

    - by NeilHambly
    I will not go into a full discussion as to why you would want to convert HEAP into a Clustered table .. as there are plenty of resources out there that describe those elements and the relevant Pro's & Con's However you may just want to understand which database tables are of the HEAP variety and how many of them "percentage wise" exist in each of your Databases So here is a useful script I have (it uses the sp_msforeachDB to iterate through all DBs on an instance), that easily...(read more)

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  • how search engines see reciprical links

    - by sam
    reciprical links cancel each other out from a search engines point of view but what counts as a recpirical link .. Do reciprical links work on a site level or an individual page level ? If you where to say get an in bound link from site-a.com to mysite.com and then linked back from blog.yoursite.com would that be reciprical. Im aware google sees subdomains as different domains all together but in this instance is that the same ?

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  • How to execute a Ruby file in Java, capable of calling functions from the Java program and receiving primitive-type results?

    - by Omega
    I do not fully understand what am I asking (lol!), well, in the sense of if it is even possible, that is. If it isn't, sorry. Suppose I have a Java program. It has a Main and a JavaCalculator class. JavaCalculator has some basic functions like public int sum(int a,int b) { return a + b } Now suppose I have a ruby file. Called MyProgram.rb. MyProgram.rb may contain anything you could expect from a ruby program. Let us assume it contains the following: class RubyMain def initialize print "The sum of 5 with 3 is #{sum(5,3)}" end def sum(a,b) # <---------- Something will happen here end end rubyMain = RubyMain.new Good. Now then, you might already suspect what I want to do: I want to run my Java program I want it to execute the Ruby file MyProgram.rb When the Ruby program executes, it will create an instance of JavaCalculator, execute the sum function it has, get the value, and then print it. The ruby file has been executed successfully. The Java program closes. Note: The "create an instance of JavaCalculator" is not entirely necessary. I would be satisfied with just running a sum function from, say, the Main class. My question: is such possible? Can I run a Java program which internally executes a Ruby file which is capable of commanding the Java program to do certain things and get results? In the above example, the Ruby file asks the Java program to do a sum for it and give the result. This may sound ridiculous. I am new in this kind of thing (if it is possible, that is). WHY AM I ASKING THIS? I have a Java program, which is some kind of game engine. However, my target audience is a bunch of Ruby coders. I don't want to have them learn Java at all. So I figured that perhaps the Java program could simply offer the functionality (capacity to create windows, display sprites, play sounds...) and then, my audience can simply code with Ruby the logic, which basically justs asks my Java engine to do things like displaying sprites or playing sounds. That's when I though about asking this.

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  • In esenthel engine how can I remove some object from Gui class?

    - by Gajet
    I know many people in this site may not know esenthel engine at all and my question may be better answered at engine forum but I'm putting it here to share the name of a real easy to code gameengine with all of you: you can easily add a Button for example to your GUI class (gui is it's shared instance) with Gui += buttonInstance.create("click on me") but I'm just wondering how can you remove an on object from from Gui members. as far as I know there is no such a method as removeChild or getChildren or anything similar.

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  • Adding a SQL Server Membership Provider using the aspnet_regsql.exe Utility

    - by nannette
    You may add a SQL Server Membership Provider using the aspnet_regsql.exe Utility on either your SQL Server Express local database or on a full-blown SQL Server database . In both implementations, you would use the aspnet_regsql.exe utility. This tool is installed when you install your .NET Framework. To use this on your SQL Server 2008 database server, for instance, you would need to first download and install the .NET Framework onto your server. Then you would need to find the location of the aspnet_regsql...(read more)

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  • Simple CMS for clients?

    - by jae
    I'm looking for something fairly simple for clients to use and very easy for me to skin (somewhat complicated themes). something like Perch or Couchcms, but has to be open source to satisfy some license requirements.. I can't really seem to find any CMS that is like this {Wordpress, drupal etc are way too heavy for this use} , really appreciated There aren't much requirements, anything will really work - each site gets their own jailed instance and stuff, just PHP/MySQL

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  • How to Choose a Web Design Company

    There are certain things that you should take into consideration, if you want to choose an apt Web Design Company, which would fulfill your business requirements. In the first instance, you should ca... [Author: Andrew Burt - Web Design and Development - June 06, 2010]

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  • Creating smooth lighting transitions using tiles in HTML5/JavaScript game

    - by user12098
    I am trying to implement a lighting effect in an HTML5/JavaScript game using tile replacement. What I have now is kind of working, but the transitions do not look smooth/natural enough as the light source moves around. Here's where I am now: Right now I have a background map that has a light/shadow spectrum PNG tilesheet applied to it - going from darkest tile to completely transparent. By default the darkest tile is drawn across the entire level on launch, covering all other layers etc. I am using my predetermined tile sizes (40 x 40px) to calculate the position of each tile and store its x and y coordinates in an array. I am then spawning a transparent 40 x 40px "grid block" entity at each position in the array The engine I'm using (ImpactJS) then allows me to calculate the distance from my light source entity to every instance of this grid block entity. I can then replace the tile underneath each of those grid block tiles with a tile of the appropriate transparency. Currently I'm doing the calculation like this in each instance of the grid block entity that is spawned on the map: var dist = this.distanceTo( ig.game.player ); var percentage = 100 * dist / 960; if (percentage < 2) { // Spawns tile 64 of the shadow spectrum tilesheet at the specified position ig.game.backgroundMaps[2].setTile( this.pos.x, this.pos.y, 64 ); } else if (percentage < 4) { ig.game.backgroundMaps[2].setTile( this.pos.x, this.pos.y, 63 ); } else if (percentage < 6) { ig.game.backgroundMaps[2].setTile( this.pos.x, this.pos.y, 62 ); } // etc... (sorry about the weird spacing, I still haven't gotten the hang of pasting code in here properly) The problem is that like I said, this type of calculation does not make the light source look very natural. Tile switching looks too sharp whereas ideally they would fade in and out smoothly using the spectrum tilesheet (I copied the tilesheet from another game that manages to do this, so I know it's not a problem with the tile shades. I'm just not sure how the other game is doing it). I'm thinking that perhaps my method of using percentages to switch out tiles could be replaced with a better/more dynamic proximity forumla of some sort that would allow for smoother transitions? Might anyone have any ideas for what I can do to improve the visuals here, or a better way of calculating proximity with the information I'm collecting about each tile? (PS: I'm reposting this from Stack Overflow at someone's suggestion, sorry about the duplicate!)

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  • Does the Adblock Plus extension prevent malicious code from downloading/executing? [closed]

    - by nctrnl
    Firefox and Chrome are my favourite browsers. The main reason is an extension called Adblock Plus. Basically, it blocks all the ad networks if you subscribe to one of the lists, like EasyList. Does it also protect against malicious ads on completely legitimate websites? For instance, several news websites use ad services that may allow a malicious user to insert "evil code". This makes the web very unsafe, especially for those who lack a serious antivirus product.

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  • Stairway to XML: Level 5 - The XML exist() and nodes() Methods

    The XML exist() method is used, often in a WHERE clause, to check the existence of an element within an XML document or fragment. The nodes() method lets you shred an XML instance and return the information as relational data. 12 essential tools for database professionalsThe SQL Developer Bundle contains 12 tools designed with the SQL Server developer and DBA in mind. Try it now.

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  • Why enumerator structs are a really bad idea (redux)

    - by Simon Cooper
    My previous blog post went into some detail as to why calling MoveNext on a BCL generic collection enumerator didn't quite do what you thought it would. This post covers the Reset method. To recap, here's the simple wrapper around a linked list enumerator struct from my previous post (minus the readonly on the enumerator variable): sealed class EnumeratorWrapper : IEnumerator<int> { private LinkedList<int>.Enumerator m_Enumerator; public EnumeratorWrapper(LinkedList<int> linkedList) { m_Enumerator = linkedList.GetEnumerator(); } public int Current { get { return m_Enumerator.Current; } } object System.Collections.IEnumerator.Current { get { return Current; } } public bool MoveNext() { return m_Enumerator.MoveNext(); } public void Reset() { ((System.Collections.IEnumerator)m_Enumerator).Reset(); } public void Dispose() { m_Enumerator.Dispose(); } } If you have a look at the Reset method, you'll notice I'm having to cast to IEnumerator to be able to call Reset on m_Enumerator. This is because the implementation of LinkedList<int>.Enumerator.Reset, and indeed of all the other Reset methods on the BCL generic collection enumerators, is an explicit interface implementation. However, IEnumerator is a reference type. LinkedList<int>.Enumerator is a value type. That means, in order to call the reset method at all, the enumerator has to be boxed. And the IL confirms this: .method public hidebysig newslot virtual final instance void Reset() cil managed { .maxstack 8 L_0000: nop L_0001: ldarg.0 L_0002: ldfld valuetype [System]System.Collections.Generic.LinkedList`1/Enumerator<int32> EnumeratorWrapper::m_Enumerator L_0007: box [System]System.Collections.Generic.LinkedList`1/Enumerator<int32> L_000c: callvirt instance void [mscorlib]System.Collections.IEnumerator::Reset() L_0011: nop L_0012: ret } On line 0007, we're doing a box operation, which copies the enumerator to a reference object on the heap, then on line 000c calling Reset on this boxed object. So m_Enumerator in the wrapper class is not modified by the call the Reset. And this is the only way to call the Reset method on this variable (without using reflection). Therefore, the only way that the collection enumerator struct can be used safely is to store them as a boxed IEnumerator<T>, and not use them as value types at all.

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