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  • Math major as a viable degree

    - by Zak O'Keefe
    While I realize there are many topics about CS vs software engineering vs game school programs, I haven't found anything relating to whether pure math degrees (with CS minor and electives) would also be a viable program. By this I mean: Would having a math major, CS minor put one at competitive disadvantage as compared to a pure CS program? This relates specifically to game engine programming, more on the graphics side. Background (for those who care): Currently a math major, CS minor at school and looking to land a career doing graphics engine programming. Admittedly, I love math and if at all possible would like to stay my current program as long as it doesn't put me at a competitive disadvantage trying to land a job post-graduation. That being said, I'm strong in the traditional C/C++ languages, strong concurrent programming skills, and currently produce self-made games for iOS. As an employer, how badly is the math major hurting me? Just want to get some advice from people already in the field!

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  • What classes are useful for an aspiring software developer? [closed]

    - by Anonymouse
    I'm a freshman in college trying to graduate in 3 years with a Math/CS dual major, and I don't have a lot of time to be fooling around with useless classes. I've tested out of most of my gen eds and science-y courses, but I need to know: what math and cs courses are most important for someone interested in algorithm development? Math courses already taken: Calc I-III,Linear Algebra, Discrete Math. CS courses taken: Java. Math courses I'm planning to take: ODE, Linear Algebra II, Vector calc, Logic, (Analysis or Algebra), Stats, probability CS courses I'm planning to take: C(required), Data Structures, Numerical Methods, Intro to Analysis of Algorithms. Which is better, analysis or algebra? Did I take enough CS courses? Am I missing out on anything? Thanks.

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  • Is this a bad time to be majoring in computer science?

    - by ATMathew
    There has been a lot of media attention paid in recent months and years to the increase in CS majors and the possibility of a second tech bubble. Some news reports have suggested that as more people enter CS, the market could be flooded with CS professionals and jobs could be increasingly difficult to find. Is this a bad time to be majoring in computer science? Edit: I'm a non-trad student who allready has a Bachelor's degree in economics and will be pursuing a CS degree starting this upcoming summer semester at the Univ of Kansas. I've been programming for about two/three years and just need a more formal education to fill the holes in my head. I have an interest in CS, it's just that I am worries about the prospects for the future.

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  • Using Repository and Unit of Work patterns with Entity Framework 4.0 and MVC 2

    - by Mr. D
    Hi, I'm following this article Using Repository and Unit of Work patterns with Entity Framework 4.0. I'm tying to implement the Repository and Unit of work pattern, using Asp.Net MVC 2 and Entity Framework 4. Please let me know if I'm doing it right... In the Models folder: Northwind.edmx Products.cs (POCO class) ProductRepository.cs (Did my product query) IProductRepository.cs NorthwindContext.cs IUnitOfWork.cs In the Controller folder: ProductController.cs (Retrieve from ProductRepository.cs and Pass it to the view) When I run the application, I'm getting error message: Mapping and metadata information could not be found for EntityType 'NorthwindMvcPoco.Models.Category'. I don't know what I'm doing wrong. I search through whole web and I couldn't resolve this issue. Please help me.

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  • TLFTextfield broken after upgrading from CS5 to CS5.5

    - by Ashley Muller
    For my project I am using the following: FlashDevelop 3.3.4 RTM Flash Pro CS 5 (libraries only, no code) Some time ago we started using TLFTextfields. One of the things I had to do was include the tlfruntime.swc file from the Adobe Flash CS 5 folder in the FlashDevelop project. Note that I copied this file to the project folder and included it, I didn't just include the file straight from the CS5 path. I have since been given a new computer that has Flash CS 5.5. I recompiled one of my swf libraries in CS 5.5, and now when I run the program, I get: Illegal override of createTextLine in flashx.textLayout.compose.ComposeState I figure the tlfruntime.swc being included in the FlashDevelop project is out of date and needs to be updated with the one from CS 5.5. So I copied the tlfruntime.swc from the CS 5.5 path, include it in the FlashDevelop project (instead of the older file), but now I get this: Illegal override of softKeyboardActivatingHandler in fl.text.container.TLFContainerController. Can anyone assist with what else I need to do to get TLFTextfields working again in CS 5.5?

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  • How to call method written in C# class library from Silver light application(xaml.cs file) ?

    - by Shyju
    Can a xaml.cs file call the method in a c# class library ? I am trying to add a Silver light control to my Existing ASP.NET project where i used to add reference to my BL Project and acces methods of BL from My UI pages of ASP.NET Web application.Now i have added one Silver light project to my solution.How can i use the already existing BL method which is in a C# class library ? When tried to add reference, it is saying that "You can only add project reference to other silver light projects in the solution". Should i give up ? Is there any way to get rid of this ?

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  • Python/PyParsing: Difficulty with setResultsName

    - by Rosarch
    I think I'm making a mistake in how I call setResultsName(): from pyparsing import * DEPT_CODE = Regex(r'[A-Z]{2,}').setResultsName("Dept Code") COURSE_NUMBER = Regex(r'[0-9]{4}').setResultsName("Course Number") COURSE_NUMBER.setParseAction(lambda s, l, toks : int(toks[0])) course = DEPT_CODE + COURSE_NUMBER course.setResultsName("course") statement = course From IDLE: >>> myparser import * >>> statement.parseString("CS 2110") (['CS', 2110], {'Dept Code': [('CS', 0)], 'Course Number': [(2110, 1)]}) The output I hope for: >>> myparser import * >>> statement.parseString("CS 2110") (['CS', 2110], {'Course': ['CS', 2110], 'Dept Code': [('CS', 0)], 'Course Number': [(2110, 1)]}) Does setResultsName() only work for terminals?

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  • Call non-static method in server side(aspx.cs) from client side use javascript (aspx).....

    - by Pramulia
    how Call non-static method in server side(aspx.cs) from client side using javascript (aspx)....? As far as I know I can call static method in server side from client side... server side : [System.Web.Services.WebMethod] public static void method1() { } client side : <script language="JavaScript"> function keyUP() { PageMethods.method1(); } </script> <asp:ScriptManager ID="ScriptManager1" runat="server" EnablePageMethods="true"> </asp:ScriptManager> It works. Now how do I call non-static method from client side...?

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  • Best way to merge two identical ASPNET web sites?

    - by ase69s
    We have two websites which only diference is in the design (Diferent images, styles, layouts..etc) but the web structure of files and cs code is the same so we want to simplify its manteinance... The actual structure would be: DefaultA.aspx DefaultA.aspx.cs DefaultB.aspx DefaultB.aspx.cs LoginA.aspx LoginA.aspx.cs LoginB.aspx LoginB.aspx.cs One idea would be changing the design differencies at runtime depending of the origin website, but we dont like much this because performance, abstraction in designing them and url confusion... Another one is sharing the cs (both aspx inheriting and using the same cs) file but we never have done or seen it done in any website before so we wonder if its a good aproach... What do you think? Any other way better in terms of performance vs development-ease?

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  • Using IIS Logs for Performance Testing with Visual Studio

    - by Tarun Arora
    In this blog post I’ll show you how you can play back the IIS Logs in Visual Studio to automatically generate the web performance tests. You can also download the sample solution I am demo-ing in the blog post. Introduction Performance testing is as important for new websites as it is for evolving websites. If you already have your website running in production you could mine the information available in IIS logs to analyse the dense zones (most used pages) and performance test those pages rather than wasting time testing & tuning the least used pages in your application. What are IIS Logs To help with server use and analysis, IIS is integrated with several types of log files. These log file formats provide information on a range of websites and specific statistics, including Internet Protocol (IP) addresses, user information and site visits as well as dates, times and queries. If you are using IIS 7 and above you will find the log files in the following directory C:\Interpub\Logs\ Walkthrough 1. Download and Install Log Parser from the Microsoft download Centre. You should see the LogParser.dll in the install folder, the default install location is C:\Program Files (x86)\Log Parser 2.2. LogParser.dll gives us a library to query the iis log files programmatically. By the way if you haven’t used Log Parser in the past, it is a is a powerful, versatile tool that provides universal query access to text-based data such as log files, XML files and CSV files, as well as key data sources on the Windows operating system such as the Event Log, the Registry, the file system, and Active Directory. More details… 2. Create a new test project in Visual Studio. Let’s call it IISLogsToWebPerfTestDemo.   3.  Delete the UnitTest1.cs class that gets created by default. Right click the solution and add a project of type class library, name it, IISLogsToWebPerfTestEngine. Delete the default class Program.cs that gets created with the project. 4. Under the IISLogsToWebPerfTestEngine project add a reference to Microsoft.VisualStudio.QualityTools.WebTestFramework – c:\Program Files (x86)\Microsoft Visual Studio 10.0\Common7\IDE\PublicAssemblies\Microsoft.VisualStudio.QualityTools.WebTestFramework.dll LogParser also called MSUtil - c:\users\tarora\documents\visual studio 2010\Projects\IisLogsToWebPerfTest\IisLogsToWebPerfTestEngine\obj\Debug\Interop.MSUtil.dll 5. Right click IISLogsToWebPerfTestEngine project and add a new classes – IISLogReader.cs The IISLogReader class queries the iis logs using the log parser. using System; using System.Collections.Generic; using System.Text; using MSUtil; using LogQuery = MSUtil.LogQueryClassClass; using IISLogInputFormat = MSUtil.COMIISW3CInputContextClassClass; using LogRecordSet = MSUtil.ILogRecordset; using Microsoft.VisualStudio.TestTools.WebTesting; using System.Diagnostics; namespace IisLogsToWebPerfTestEngine { // By making use of log parser it is possible to query the iis log using select queries public class IISLogReader { private string _iisLogPath; public IISLogReader(string iisLogPath) { _iisLogPath = iisLogPath; } public IEnumerable<WebTestRequest> GetRequests() { LogQuery logQuery = new LogQuery(); IISLogInputFormat iisInputFormat = new IISLogInputFormat(); // currently these columns give us suffient information to construct the web test requests string query = @"SELECT s-ip, s-port, cs-method, cs-uri-stem, cs-uri-query FROM " + _iisLogPath; LogRecordSet recordSet = logQuery.Execute(query, iisInputFormat); // Apply a bit of transformation while (!recordSet.atEnd()) { ILogRecord record = recordSet.getRecord(); if (record.getValueEx("cs-method").ToString() == "GET") { string server = record.getValueEx("s-ip").ToString(); string path = record.getValueEx("cs-uri-stem").ToString(); string querystring = record.getValueEx("cs-uri-query").ToString(); StringBuilder urlBuilder = new StringBuilder(); urlBuilder.Append("http://"); urlBuilder.Append(server); urlBuilder.Append(path); if (!String.IsNullOrEmpty(querystring)) { urlBuilder.Append("?"); urlBuilder.Append(querystring); } // You could make substitutions by introducing parameterized web tests. WebTestRequest request = new WebTestRequest(urlBuilder.ToString()); Debug.WriteLine(request.UrlWithQueryString); yield return request; } recordSet.moveNext(); } Console.WriteLine(" That's it! Closing the reader"); recordSet.close(); } } }   6. Connect the dots by adding the project reference ‘IisLogsToWebPerfTestEngine’ to ‘IisLogsToWebPerfTest’. Right click the ‘IisLogsToWebPerfTest’ project and add a new class ‘WebTest1Coded.cs’ The WebTest1Coded.cs inherits from the WebTest class. By overriding the GetRequestMethod we can inject the log files to the IISLogReader class which uses Log parser to query the log file and extract the web requests to generate the web test request which is yielded back for play back when the test is run. namespace IisLogsToWebPerfTest { using System; using System.Collections.Generic; using System.Text; using Microsoft.VisualStudio.TestTools.WebTesting; using Microsoft.VisualStudio.TestTools.WebTesting.Rules; using IisLogsToWebPerfTestEngine; // This class is a coded web performance test implementation, that simply passes // the path of the iis logs to the IisLogReader class which does the heavy // lifting of reading the contents of the log file and converting them to tests. // You could have multiple such classes that inherit from WebTest and implement // GetRequestEnumerator Method and pass differnt log files for different tests. public class WebTest1Coded : WebTest { public WebTest1Coded() { this.PreAuthenticate = true; } public override IEnumerator<WebTestRequest> GetRequestEnumerator() { // substitute the highlighted path with the path of the iis log file IISLogReader reader = new IISLogReader(@"C:\Demo\iisLog1.log"); foreach (WebTestRequest request in reader.GetRequests()) { yield return request; } } } }   7. Its time to fire the test off and see the iis log playback as a web performance test. From the Test menu choose Test View Window you should be able to see the WebTest1Coded test show up. Highlight the test and press Run selection (you can also debug the test in case you face any failures during test execution). 8. Optionally you can create a Load Test by keeping ‘WebTest1Coded’ as the base test. Conclusion You have just helped your testing team, you now have become the coolest developer in your organization! Jokes apart, log parser and web performance test together allow you to save a lot of time by not having to worry about what to test or even worrying about how to record the test. If you haven’t already, download the solution from here. You can take this to the next level by using LogParser to extract the log files as part of an end of day batch to a database. See the usage trends by user this solution over a longer term and have your tests consume the web requests now stored in the database to generate the web performance tests. If you like the post, don’t forget to share … Keep RocKiNg!

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  • I need some career/education advice regarding computer science [on hold]

    - by user2521987
    So I'm a senior mathematics major this fall and I have only taken three CS classes (Java I, Java II, and C++). This summer, I am participating in a mathematics REU (Research Experience for Undergraduates), and I program in C++ about 8 hours a day...and I find that I absolutely love it. I love using programming to solve math problems in my research. I think I want to pursue a career in programming. I have a few options Stay at my university an extra 1-1.5 years (beyond the 4) and do a double major in Math/CS. This will put me in up to around 7-10k in debt (currently I have no debt and am scheduled to graduate debt free). Then apply to a masters in CS. Apply directly to a masters in CS from a math undergraduate degree. I don't like this idea because I likely won't get into a good program or funded with such little background. Go to graduate school, funded, in applied mathematics and try to further my knowledge in computer science while there. Then apply to a masters in CS. I'm not sure if 1 or 3 would be better. My end goal would be to go to a top 20-30 CS graduate program and to get a cool, good job. What would you recommend?

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  • How to create a class by reading from another class (.cs) file with Powershell?

    - by Razcer
    I have this POGO ( simple putter getter) class that I am trying to read in PowerShell using System; using System.Runtime.Serialization; namespace MyApp.VM { [Serializable] public class MyClassVM { public Int64 CtrId { get; set; } public string CtrName { get; set; } public string CtrPhone { get; set; } public string CtrZip { get; set; } public DateTime AddDate { get; set; } } } Here is the ps1 code that is trying to read the class from a file. function Build-Pogo { $FileDir = "D:\YourDirectoryOfPogo" $ClassName = "MyClassVM" $FileName = $FileDir + "\" + $ClassName + ".cs" # Build the class from the file $AllLines = [string]::join([environment]::newline, (Get-Content $FileName)) Add-Type -TypeDefinition $AllLines # spin thru each property for class $ClassHandle = New-Object -typeName $ClassName $ClassHandle | ForEach-Object {Write-Host $_.name -foregroundcolor cyan} } *Note the last line is placeholder for more complex logic to come later. This breaks at the Add-Type with this error message for each get/set in the file. 'MyApp.VM.MyClassVM.CtrId.get' must declare a body because it is not marked abstract or extern Any info on what I'm doing wrong will be greatly appreciated.

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  • NHibernate.MappingException: No persister for:

    - by Sara Chipps
    Now, before you say it I DID google and my hbm.xml file IS an Embedded Resource. Here is the code I am calling: ISession session = GetCurrentSession(); var returnObject = session.Get<T>(Id); Here is my mapping file for the class: <?xml version="1.0" encoding="utf-8" ?> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"> <class name="HQData.Objects.SubCategory, HQData" table="SubCategory" lazy="true"> <id name="ID" column="ID" unsaved-value="0"> <generator class="identity" /> </id> <property name="Name" column="Name" /> <property name="NumberOfBuckets" column="NumberOfBuckets" /> <property name="SearchCriteriaOne" column="SearchCriteriaOne" /> <bag name="_Businesses" cascade="all"> <key column="SubCategoryId"/> <one-to-many class="HQData.Objects.Business, HQData"/> </bag> <bag name="_Buckets" cascade="all"> <key column="SubCategoryId"/> <one-to-many class="HQData.Objects.Bucket, HQData"/> </bag> </class> </hibernate-mapping> Has anyone run to this issue before? I swore that was it after I read it, but no dice. Here is the rest of the error and thanks for your help. MappingException: No persister for: HQData.Objects.SubCategory]NHibernate.Impl.SessionFactoryImpl.GetEntityPersister(String entityName, Boolean throwIfNotFound) in c:\CSharp\NH2.0.0\nhibernate\src\NHibernate\Impl\SessionFactoryImpl.cs:766 NHibernate.Impl.SessionFactoryImpl.GetEntityPersister(String entityName) in c:\CSharp\NH2.0.0\nhibernate\src\NHibernate\Impl\SessionFactoryImpl.cs:752 NHibernate.Event.Default.DefaultLoadEventListener.OnLoad(LoadEvent event, LoadType loadType) in c:\CSharp\NH2.0.0\nhibernate\src\NHibernate\Event\Default\DefaultLoadEventListener.cs:37 NHibernate.Impl.SessionImpl.FireLoad(LoadEvent event, LoadType loadType) in c:\CSharp\NH2.0.0\nhibernate\src\NHibernate\Impl\SessionImpl.cs:2054 NHibernate.Impl.SessionImpl.Get(String entityName, Object id) in c:\CSharp\NH2.0.0\nhibernate\src\NHibernate\Impl\SessionImpl.cs:1029 NHibernate.Impl.SessionImpl.Get(Type entityClass, Object id) in c:\CSharp\NH2.0.0\nhibernate\src\NHibernate\Impl\SessionImpl.cs:1020 NHibernate.Impl.SessionImpl.Get(Object id) in c:\CSharp\NH2.0.0\nhibernate\src\NHibernate\Impl\SessionImpl.cs:985 HQData.DataAccessUtils.NHibernateObjectHelper.LoadDataObject(Int32 Id) in C:\Development\HQChannelRepo\HQ Channel Application\HQChannel\HQData\DataAccessUtils\NHibernateObjectHelper.cs:42 HQWebsite.LocalSearch.get_subCategory() in C:\Development\HQChannelRepo\HQ Channel Application\HQChannel\HQWebsite\LocalSearch.aspx.cs:17 HQWebsite.LocalSearch.Page_Load(Object sender, EventArgs e) in C:\Development\HQChannelRepo\HQ Channel Application\HQChannel\HQWebsite\LocalSearch.aspx.cs:27 System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +15 System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +33 System.Web.UI.Control.OnLoad(EventArgs e) +99 System.Web.UI.Control.LoadRecursive() +47 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1436 I had changed some code and I wasn't adding the Assembly to the config file during runtime. Thanks for your help This has been fixed, I am not F-ing with my NHibernate setup ever again!

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  • Visual Studio File Groupings

    - by Daniel
    In Visual Studio 3 files are typically grouped together: filename.aspx filename.aspx.cs filename.aspx.designer.cs Is there a way to add another file that grouping so that it can be collapsed and out of view? filename.aspx filename.aspx.cs filename.aspx.designer.cs customfile.cs Thanks

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  • Hardware Pen device for presentation

    - by sankar
    Hi I have a scenario. Hope you could suggest the software and hardware required? I teach maths. I write math equations as i do in a paper/ohp and this should get displayed on the screen. I find hardware 'pen' - writing and pointing device. Tablet pen- I accept my limited knowledge on that. Here is how I conceive it could be done? I need you to correct my understanding and shed light anyother better method? tablet pen - plate (on which i write) - ms-powerpoint pen option - empty slide Is it possible to save the such content for reproduction. regds, sankar

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  • Embedding mercurial revision information in Visual Studio c# projects automatically

    - by Mark Booth
    Original Problem In building our projects, I want the mercurial id of each repository to be embedded within the product(s) of that repository (the library, application or test application). I find it makes it so much easier to debug an application ebing run by custiomers 8 timezones away if you know precisely what went into building the particular version of the application they are using. As such, every project (application or library) in our systems implement a way of getting at the associated revision information. I also find it very useful to be able to see if an application has been compiled with clean (un-modified) changesets from the repository. 'Hg id' usefully appends a + to the changeset id when there are uncommitted changes in a repository, so this allows is to easily see if people are running a clean or a modified version of the code. My current solution is detailed below, and fulfills the basic requirements, but there are a number of problems with it. Current Solution At the moment, to each and every Visual Studio solution, I add the following "Pre-build event command line" commands: cd $(ProjectDir) HgID I also add an HgID.bat file to the Project directory: @echo off type HgId.pre > HgId.cs For /F "delims=" %%a in ('hg id') Do <nul >>HgID.cs set /p = @"%%a" echo ; >> HgId.cs echo } >> HgId.cs echo } >> HgId.cs along with an HgId.pre file, which is defined as: namespace My.Namespace { /// <summary> Auto generated Mercurial ID class. </summary> internal class HgID { /// <summary> Mercurial version ID [+ is modified] [Named branch]</summary> public const string Version = When I build my application, the pre-build event is triggered on all libraries, creating a new HgId.cs file (which is not kept under revision control) and causing the library to be re-compiled with with the new 'hg id' string in 'Version'. Problems with the current solution The main problem is that since the HgId.cs is re-created at each pre-build, every time we need to compile anything, all projects in the current solution are re-compiled. Since we want to be able to easily debug into our libraries, we usually keep many libraries referenced in our main application solution. This can result in build times which are significantly longer than I would like. Ideally I would like the libraries to compile only if the contents of the HgId.cs file has actually changed, as opposed to having been re-created with exactly the same contents. The second problem with this method is it's dependence on specific behaviour of the windows shell. I've already had to modify the batch file several times, since the original worked under XP but not Vista, the next version worked under Vista but not XP and finally I managed to make it work with both. Whether it will work with Windows 7 however is anyones guess and as time goes on, I see it more likely that contractors will expect to be able to build our apps on their Windows 7 boxen. Finally, I have an aesthetic problem with this solution, batch files and bodged together template files feel like the wrong way to do this. My actual questions How would you solve/how are you solving the problem I'm trying to solve? What better options are out there than what I'm currently doing? Rejected Solutions to these problems Before I implemented the current solution, I looked at Mercurials Keyword extension, since it seemed like the obvious solution. However the more I looked at it and read peoples opinions, the more that I came to the conclusion that it wasn't the right thing to do. I also remember the problems that keyword substitution has caused me in projects at previous companies (just the thought of ever having to use Source Safe again fills me with a feeling of dread *8'). Also, I don't particularly want to have to enable Mercurial extensions to get the build to complete. I want the solution to be self contained, so that it isn't easy for the application to be accidentally compiled without the embedded version information just because an extension isn't enabled or the right helper software hasn't been installed. I also thought of writing this in a better scripting language, one where I would only write HgId.cs file if the content had actually changed, but all of the options I could think of would require my co-workers, contractors and possibly customers to have to install software they might not otherwise want (for example cygwin). Any other options people can think of would be appreciated. Update Partial solution Having played around with it for a while, I've managed to get the HgId.bat file to only overwrite the HgId.cs file if it changes: @echo off type HgId.pre > HgId.cst For /F "delims=" %%a in ('hg id') Do <nul >>HgId.cst set /p = @"%%a" echo ; >> HgId.cst echo } >> HgId.cst echo } >> HgId.cst fc HgId.cs HgId.cst >NUL if %errorlevel%==0 goto :ok copy HgId.cst HgId.cs :ok del HgId.cst Problems with this solution Even though HgId.cs is no longer being re-created every time, Visual Studio still insists on compiling everything every time. I've tried looking for solutions and tried checking "Only build startup projects and dependencies on Run" in Tools|Options|Projects and Solutions|Build and Run but it makes no difference. The second problem also remains, and now I have no way to test if it will work with Vista, since that contractor is no longer with us. If anyone can test this batch file on a Windows 7 and/or Vista box, I would appreciate hearing how it went. Finally, my aesthetic problem with this solution, is even strnger than it was before, since the batch file is more complex and this there is now more to go wrong. If you can think of any better solution, I would love to hear about them.

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  • Why enumerator structs are a really bad idea

    - by Simon Cooper
    If you've ever poked around the .NET class libraries in Reflector, I'm sure you would have noticed that the generic collection classes all have implementations of their IEnumerator as a struct rather than a class. As you will see, this design decision has some rather unfortunate side effects... As is generally known in the .NET world, mutable structs are a Very Bad Idea; and there are several other blogs around explaining this (Eric Lippert's blog post explains the problem quite well). In the BCL, the generic collection enumerators are all mutable structs, as they need to keep track of where they are in the collection. This bit me quite hard when I was coding a wrapper around a LinkedList<int>.Enumerator. It boils down to this code: sealed class EnumeratorWrapper : IEnumerator<int> { private readonly 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(); } } The key line here is the MoveNext method. When I initially coded this, I thought that the call to m_Enumerator.MoveNext() would alter the enumerator state in the m_Enumerator class variable and so the enumeration would proceed in an orderly fashion through the collection. However, when I ran this code it went into an infinite loop - the m_Enumerator.MoveNext() call wasn't actually changing the state in the m_Enumerator variable at all, and my code was looping forever on the first collection element. It was only after disassembling that method that I found out what was going on The MoveNext method above results in the following IL: .method public hidebysig newslot virtual final instance bool MoveNext() cil managed { .maxstack 1 .locals init ( [0] bool CS$1$0000, [1] valuetype [System]System.Collections.Generic.LinkedList`1/Enumerator CS$0$0001) L_0000: nop L_0001: ldarg.0 L_0002: ldfld valuetype [System]System.Collections.Generic.LinkedList`1/Enumerator EnumeratorWrapper::m_Enumerator L_0007: stloc.1 L_0008: ldloca.s CS$0$0001 L_000a: call instance bool [System]System.Collections.Generic.LinkedList`1/Enumerator::MoveNext() L_000f: stloc.0 L_0010: br.s L_0012 L_0012: ldloc.0 L_0013: ret } Here, the important line is 0002 - m_Enumerator is accessed using the ldfld operator, which does the following: Finds the value of a field in the object whose reference is currently on the evaluation stack. So, what the MoveNext method is doing is the following: public bool MoveNext() { LinkedList<int>.Enumerator CS$0$0001 = this.m_Enumerator; bool CS$1$0000 = CS$0$0001.MoveNext(); return CS$1$0000; } The enumerator instance being modified by the call to MoveNext is the one stored in the CS$0$0001 variable on the stack, and not the one in the EnumeratorWrapper class instance. Hence why the state of m_Enumerator wasn't getting updated. Hmm, ok. Well, why is it doing this? If you have a read of Eric Lippert's blog post about this issue, you'll notice he quotes a few sections of the C# spec. In particular, 7.5.4: ...if the field is readonly and the reference occurs outside an instance constructor of the class in which the field is declared, then the result is a value, namely the value of the field I in the object referenced by E. And my m_Enumerator field is readonly! Indeed, if I remove the readonly from the class variable then the problem goes away, and the code works as expected. The IL confirms this: .method public hidebysig newslot virtual final instance bool MoveNext() cil managed { .maxstack 1 .locals init ( [0] bool CS$1$0000) L_0000: nop L_0001: ldarg.0 L_0002: ldflda valuetype [System]System.Collections.Generic.LinkedList`1/Enumerator EnumeratorWrapper::m_Enumerator L_0007: call instance bool [System]System.Collections.Generic.LinkedList`1/Enumerator::MoveNext() L_000c: stloc.0 L_000d: br.s L_000f L_000f: ldloc.0 L_0010: ret } Notice on line 0002, instead of the ldfld we had before, we've got a ldflda, which does this: Finds the address of a field in the object whose reference is currently on the evaluation stack. Instead of loading the value, we're loading the address of the m_Enumerator field. So now the call to MoveNext modifies the enumerator stored in the class rather than on the stack, and everything works as expected. Previously, I had thought enumerator structs were an odd but interesting feature of the BCL that I had used in the past to do linked list slices. However, effects like this only underline how dangerous mutable structs are, and I'm at a loss to explain why the enumerators were implemented as structs in the first place. (interestingly, the SortedList<TKey, TValue> enumerator is a struct but is private, which makes it even more odd - the only way it can be accessed is as a boxed IEnumerator!). I would love to hear people's theories as to why the enumerators are implemented in such a fashion. And bonus points if you can explain why LinkedList<int>.Enumerator.Reset is an explicit implementation but Dispose is implicit... Note to self: never ever ever code a mutable struct.

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  • how to resolve this .Net 3.5 warning/error?

    - by 5YrsLaterDBA
    I have three machines. one installed VS2008 another two installed SDK6 and Framework3.5 (one of these two is a build machine). When I use MSBuild to build our application, all of them get this warning: C:\WINDOWS\Microsoft.NET\Framework\v3.5\Microsoft.Common.targets : warning MSB3245: Could not resolve this reference. Could not locate the assembly "WPFToolkit, Version=3.5.40128.1, Culture=neutral, PublicKeyToken=31bf3856ad364e35". Check to make sure the assembly exists on disk. If this reference is required by your code, you may get compilation errors. and the build machine comes with some errors: scsm\SCSM.cs(234,13): error CS1501: No overload for method 'Invoke' takes '1' arguments scsm\SCSM.cs(235,13): error CS1501: No overload for method 'Invoke' takes '1' arguments scsm\SCSM.cs(304,13): error CS1501: No overload for method 'Invoke' takes '1' arguments scsm\SCSM.cs(314,13): error CS1501: No overload for method 'Invoke' takes '1' arguments scsm\SCSM.cs(317,13): error CS1501: No overload for method 'Invoke' takes '1' arguments scsm\SCSM.cs(323,17): error CS1501: No overload for method 'Invoke' takes '1' arguments scsm\SCSM.cs(324,17): error CS1501: No overload for method 'Invoke' takes '1' arguments scsm\SCSM.cs(325,17): error CS1501: No overload for method 'Invoke' takes '1' arguments but other machines are passed without error. Resources are identical in those three machines. searched online but cannot find answer. Anybody here can help me resolve this? thanks

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  • Mono ASP.NET Oracle Connection

    - by bladepit
    Hello to everybody, if i want to connect to orcale i became the following error: libclntsh.so Description: HTTP 500. Error processing request. Stack Trace: System.DllNotFoundException: libclntsh.so at (wrapper managed-to-native) System.Data.OracleClient.Oci.OciCalls/OciNativeCalls.OCIEnvCreate (intptr&,System.Data.OracleClient.Oci.OciEnvironmentMode,intptr,intptr,intptr,intptr,int,intptr) <0x0005d at System.Data.OracleClient.Oci.OciCalls.OCIEnvCreate (intptr&,System.Data.OracleClient.Oci.OciEnvironmentMode,intptr,intptr,intptr,intptr,int,intptr) [0x00000] in /src/monoscript/mono-2.4.2.3/mcs/class/System.Data.OracleClient/System.Data.OracleClient.Oci/OciCalls.cs:738 at System.Data.OracleClient.Oci.OciEnvironmentHandle..ctor (System.Data.OracleClient.Oci.OciEnvironmentMode) [0x00013] in /src/monoscript/mono-2.4.2.3/mcs/class/System.Data.OracleClient/System.Data.OracleClient.Oci/OciEnvironmentHandle.cs:35 at System.Data.OracleClient.Oci.OciGlue.CreateConnection (System.Data.OracleClient.OracleConnectionInfo) [0x00000] in /src/monoscript/mono-2.4.2.3/mcs/class/System.Data.OracleClient/System.Data.OracleClient/OciGlue.cs:86 at System.Data.OracleClient.OracleConnectionPoolManager.CreateConnection (System.Data.OracleClient.OracleConnectionInfo) [0x00006] in /src/monoscript/mono-2.4.2.3/mcs/class/System.Data.OracleClient/System.Data.OracleClient/OracleConnectionPoolManager.cs:57 at System.Data.OracleClient.OracleConnectionPool.CreateConnection () [0x0000e] in /src/monoscript/mono-2.4.2.3/mcs/class/System.Data.OracleClient/System.Data.OracleClient/OracleConnectionPool.cs:97 at System.Data.OracleClient.OracleConnectionPool.GetConnection () [0x000ba] in /src/monoscript/mono-2.4.2.3/mcs/class/System.Data.OracleClient/System.Data.OracleClient/OracleConnectionPool.cs:74 at System.Data.OracleClient.OracleConnection.Open () [0x00061] in /src/monoscript/mono-2.4.2.3/mcs/class/System.Data.OracleClient/System.Data.OracleClient/OracleConnection.cs:410 at WebServer.Controllers.HomeController.Index () [0x00006] in /home/bhcweb/Projects/Controllers/HomeController.cs:19 at (wrapper dynamic-method) System.Runtime.CompilerServices.ExecutionScope.lambda_method (System.Runtime.CompilerServices.ExecutionScope,System.Web.Mvc.ControllerBase,object[]) <0x00080 at System.Web.Mvc.ActionMethodDispatcher.Execute (System.Web.Mvc.ControllerBase,object[]) <0x0001b at System.Web.Mvc.ReflectedActionDescriptor.Execute (System.Web.Mvc.ControllerContext,System.Collections.Generic.IDictionary2<string, object>) <0x000fd> at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod (System.Web.Mvc.ControllerContext,System.Web.Mvc.ActionDescriptor,System.Collections.Generic.IDictionary2) <0x0001c at System.Web.Mvc.ControllerActionInvoker/c_AnonStoreyB.<m_E () <0x00067 at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter (System.Web.Mvc.IActionFilter,System.Web.Mvc.ActionExecutingContext,System.Func`1) <0x000c4 What is my Problem there? I have read that i have to set my ORACLE_HOME AND LD_LIBRARY_PATH. If i do echo $ORACLE_HOME and $LD_LIBRARY_PATH the path which i have set is coming out: /usr/lib/oracle/xe/app/oracle/product/10.2.0/client/lib This is the path where the libclntsh.so is in. Is this right? Best regards bladepit

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  • IIS6 Log time recording problems

    - by Hafthor
    On three separate occasions on two separate servers at nearly the same times, 6.9 hours seemingly went by without any data being written to the IIS logs, but, on closer inspection, it appears that it was all recorded all at once. Here's the facts as I know them: Windows Server 2003 R2 w/ IIS6 Logging using GMT, server local time GMT-7. Application was still operating and I have SQL data to prove that Time gaps appear in log file, not across two # headers appear at gap Load balancer pings every 30 seconds No caching Here's info on a particular case: an entry appears for 2009-09-21 18:09:27 then #headers the next entry is for 2009-09-22 01:21:54, and so are the next 1600 entries in this log file and 370 in the next log file. about half of the ~2000 entries on 2009-09-22 01:21:54 are load balancer pings (est. at 2/min for 6.9hrs = 828 pings) then entries are recorded as normal. I believe that these events may coincide with me deploying an ASP.NET application update into those machines. Here's some relevant content from the logs in question: ex090921.log line 3684 2009-09-21 17:54:40 GET /ping.aspx - 80 404 0 0 3733 122 0 2009-09-21 17:55:11 GET /ping.aspx - 80 404 0 0 3733 122 0 2009-09-21 17:55:42 GET /ping.aspx - 80 404 0 0 3733 122 0 2009-09-21 17:56:13 GET /ping.aspx - 80 404 0 0 3733 122 0 2009-09-21 17:56:45 GET /ping.aspx - 80 404 0 0 3733 122 0 #Software: Microsoft Internet Information Services 6.0 #Version: 1.0 #Date: 2009-09-21 18:04:37 #Fields: date time cs-method cs-uri-stem cs-uri-query s-port sc-status sc-substatus sc-win32-status sc-bytes cs-bytes time-taken 2009-09-22 01:04:06 GET /ping.aspx - 80 404 0 0 3733 122 3078 2009-09-22 01:04:06 GET /ping.aspx - 80 404 0 0 3733 122 109 2009-09-22 01:04:06 GET /ping.aspx - 80 200 0 0 278 122 3828 2009-09-22 01:04:06 GET /ping.aspx - 80 200 0 0 278 122 0 2009-09-22 01:04:06 GET /ping.aspx - 80 200 0 0 278 122 0 ... continues until line 5449 2009-09-22 01:04:06 GET /ping.aspx - 80 200 0 0 277 122 0 <eof> ex090922.log #Software: Microsoft Internet Information Services 6.0 #Version: 1.0 #Date: 2009-09-22 00:00:16 #Fields: date time cs-method cs-uri-stem cs-uri-query s-port sc-status sc-substatus sc-win32-status sc-bytes cs-bytes time-taken 2009-09-22 01:04:06 GET /ping.aspx - 80 200 0 0 277 122 0 2009-09-22 01:04:06 GET /ping.aspx - 80 200 0 0 277 122 0 ... continues until line 367 2009-09-22 01:04:06 GET /ping.aspx - 80 200 0 0 277 122 0 2009-09-22 01:04:30 GET /ping.aspx - 80 200 0 0 277 122 0 ... back to normal behavior Note the seemingly correct date/time written to the #header of the new log file. Also note that /ping.aspx returned 404 then switched to 200 just as the problem started. I rename the "I'm alive page" so the load balancer stops sending requests to the server while I'm working on it. What you see here is me renaming it back so the load balancer will use the server. So, this problem definitely coincides with me re-enabling the server. Any ideas?

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  • IIS6 Log time recording problems

    - by Hafthor
    On three separate occasions on two separate servers at nearly the same times, 6.9 hours seemingly went by without any data being written to the IIS logs, but, on closer inspection, it appears that it was all recorded all at once. Here's the facts as I know them: Windows Server 2003 R2 w/ IIS6 Logging using GMT, server local time GMT-7. Application was still operating and I have SQL data to prove that Time gaps appear in log file, not across two # headers appear at gap Load balancer pings every 30 seconds No caching Here's info on a particular case: an entry appears for 2009-09-21 18:09:27 then #headers the next entry is for 2009-09-22 01:21:54, and so are the next 1600 entries in this log file and 370 in the next log file. about half of the ~2000 entries on 2009-09-22 01:21:54 are load balancer pings (est. at 2/min for 6.9hrs = 828 pings) then entries are recorded as normal. I believe that these events may coincide with me deploying an ASP.NET application update into those machines. Here's some relevant content from the logs in question: ex090921.log line 3684 2009-09-21 17:54:40 GET /ping.aspx - 80 404 0 0 3733 122 0 2009-09-21 17:55:11 GET /ping.aspx - 80 404 0 0 3733 122 0 2009-09-21 17:55:42 GET /ping.aspx - 80 404 0 0 3733 122 0 2009-09-21 17:56:13 GET /ping.aspx - 80 404 0 0 3733 122 0 2009-09-21 17:56:45 GET /ping.aspx - 80 404 0 0 3733 122 0 #Software: Microsoft Internet Information Services 6.0 #Version: 1.0 #Date: 2009-09-21 18:04:37 #Fields: date time cs-method cs-uri-stem cs-uri-query s-port sc-status sc-substatus sc-win32-status sc-bytes cs-bytes time-taken 2009-09-22 01:04:06 GET /ping.aspx - 80 404 0 0 3733 122 3078 2009-09-22 01:04:06 GET /ping.aspx - 80 404 0 0 3733 122 109 2009-09-22 01:04:06 GET /ping.aspx - 80 200 0 0 278 122 3828 2009-09-22 01:04:06 GET /ping.aspx - 80 200 0 0 278 122 0 2009-09-22 01:04:06 GET /ping.aspx - 80 200 0 0 278 122 0 ... continues until line 5449 2009-09-22 01:04:06 GET /ping.aspx - 80 200 0 0 277 122 0 <eof> ex090922.log #Software: Microsoft Internet Information Services 6.0 #Version: 1.0 #Date: 2009-09-22 00:00:16 #Fields: date time cs-method cs-uri-stem cs-uri-query s-port sc-status sc-substatus sc-win32-status sc-bytes cs-bytes time-taken 2009-09-22 01:04:06 GET /ping.aspx - 80 200 0 0 277 122 0 2009-09-22 01:04:06 GET /ping.aspx - 80 200 0 0 277 122 0 ... continues until line 367 2009-09-22 01:04:06 GET /ping.aspx - 80 200 0 0 277 122 0 2009-09-22 01:04:30 GET /ping.aspx - 80 200 0 0 277 122 0 ... back to normal behavior Note the seemingly correct date/time written to the #header of the new log file. Also note that /ping.aspx returned 404 then switched to 200 just as the problem started. I rename the "I'm alive page" so the load balancer stops sending requests to the server while I'm working on it. What you see here is me renaming it back so the load balancer will use the server. So, this problem definitely coincides with me re-enabling the server. Any ideas?

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  • How can I extend DynamicQuery.cs to implement a .Single method?

    - by Yoenhofen
    I need to write some dynamic queries for a project I'm working on. I'm finding out that a significant amount of time is being spent by my program on the Count and First methods, so I started to change to .Single, only to find out that there is no such method. The code below was my first attempt at creating one (mostly copied from the Where method), but it's not working. Help? public static object Single(this IQueryable source, string predicate, params object[] values) { if (source == null) throw new ArgumentNullException("source"); if (predicate == null) throw new ArgumentNullException("predicate"); LambdaExpression lambda = DynamicExpression.ParseLambda(source.ElementType, typeof(bool), predicate, values); return source.Provider.CreateQuery( Expression.Call( typeof(Queryable), "Single", new Type[] { source.ElementType }, source.Expression, Expression.Quote(lambda))); }

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  • Help to translate SQL query to Relational Algebra

    - by Mestika
    Hi everyone, I'm having some difficulties with translating some queries to Relational Algebra. I've a great book about Database Design and here is a chapter about Relational Algebra but I still seem to have some trouble creating the right one: Thoes queries I've most difficuelt with is these: SELECT COUNT( cs.student_id ) AS counter FROM course c, course_student cs WHERE c.id = cs.course_id AND c.course_name = 'Introduction to Database Design' SELECT COUNT( cs.student_id ) FROM Course c INNER JOIN course_student cs ON c.id = cs.course_id WHERE c.course_name = 'Introduction to Database Design' and SELECT COUNT( * ) FROM student JOIN grade ON student.f_name = "Andreas" AND student.l_name = "Pedersen" AND student.id = grade.student_id I know the notation can be a bit hard to paste into HTML forum, but maybe just use some common name or the Greek name. Thanks in advance Mestika

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  • What are the CS fundamentals behind package/dependency management?

    - by Frep D-Oronge
    Often I hear about situations where companies are developing extensable in house software (the dreaded enterprise 'framework') which is supposed to support multiple 'plugins' from diffirent teams. Usually this ends up being a half baked solution that does not really work due to compatibility prolems between addins, or between addins and the framework itself. Usually this means QA have to 'rubber stamp' a global set of versions accross all plugins, or more usually plugins are released and stuff breaks in nasty ways. This problem has been solved before however, for example the package management systems like apt for debian linux. I suspect that the reason it works is that it is built from the start on a known 'Computer Science-y' concept. My question is what is it?

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