Crash Instantiating System.Xml.Serialization.XmlSerializer in C#.

Question

We're seeing a crash when instantiating an instance of the System.Xml.Serialization.XmlSerializer class in a C# library. The crash occurs in the constructor, when it tries to add a duplicate key to a dictionary. I've included a stack trace below.

This crash is only occurring on one machine, and repairing our installation of .NET 3.5 didn't help. Has anyone else seen any similar issues?

System.ArgumentException was unhandled
  Message="Item has already been added. Key in dictionary: 'mainbuild'  Key being added: 'mainbuild'"
  Source="mscorlib"
  StackTrace:
       at System.Collections.Hashtable.Insert(Object key, Object nvalue, Boolean add)
       at System.Collections.Hashtable.Add(Object key, Object value)
       at System.Collections.Specialized.StringDictionary.Add(String key, String value)
       at System.CodeDom.Compiler.Executor.ExecWaitWithCaptureUnimpersonated(SafeUserTokenHandle userToken, String cmd, String currentDir, TempFileCollection tempFiles, String& outputName, String& errorName, String trueCmdLine)
       at System.CodeDom.Compiler.Executor.ExecWaitWithCapture(SafeUserTokenHandle userToken, String cmd, String currentDir, TempFileCollection tempFiles, String& outputName, String& errorName, String trueCmdLine)
       at Microsoft.CSharp.CSharpCodeGenerator.Compile(CompilerParameters options, String compilerDirectory, String compilerExe, String arguments, String& outputFile, Int32& nativeReturnValue, String trueArgs)
       at Microsoft.CSharp.CSharpCodeGenerator.FromFileBatch(CompilerParameters options, String[] fileNames)
       at Microsoft.CSharp.CSharpCodeGenerator.FromSourceBatch(CompilerParameters options, String[] sources)
       at Microsoft.CSharp.CSharpCodeGenerator.System.CodeDom.Compiler.ICodeCompiler.CompileAssemblyFromSourceBatch(CompilerParameters options, String[] sources)
       at System.CodeDom.Compiler.CodeDomProvider.CompileAssemblyFromSource(CompilerParameters options, String[] sources)
       at System.Xml.Serialization.Compiler.Compile(Assembly parent, String ns, XmlSerializerCompilerParameters xmlParameters, Evidence evidence)
       at System.Xml.Serialization.TempAssembly.GenerateAssembly(XmlMapping[] xmlMappings, Type[] types, String defaultNamespace, Evidence evidence, XmlSerializerCompilerParameters parameters, Assembly assembly, Hashtable assemblies)
       at System.Xml.Serialization.TempAssembly..ctor(XmlMapping[] xmlMappings, Type[] types, String defaultNamespace, String location, Evidence evidence)
       at System.Xml.Serialization.XmlSerializer.GenerateTempAssembly(XmlMapping xmlMapping, Type type, String defaultNamespace)
       at System.Xml.Serialization.XmlSerializer..ctor(Type type, String defaultNamespace)
       at System.Xml.Serialization.XmlSerializer..ctor(Type type)
       at OurTools.Tools.Common.XML.DataAccess`1.DeserializeFromXml(String strFilePath) in c:\AutomatedBuild\projects\1.0\OurTools.Tools.Common\OurTools.Tools.Common\XML\DataAcess.cs:line 100
       at OurTools.Tools.Common.ProjectFileManager.GetProjectInfoModel() in c:\AutomatedBuild\projects\1.0\OurTools.Tools.Common\OurTools.Tools.Common\ProjectFileManager.cs:line 252
       at OurTools.Tools.Common.ProjectFileManager.GetAvailableCultures() in c:\AutomatedBuild\projects\1.0\OurTools.Tools.Common\OurTools.Tools.Common\ProjectFileManager.cs:line 299
       at OurAppLib.GeneratorOptions.DefaultCultures() in c:\AutomatedBuild\projects\1.0\OurApp\OurAppLib\GeneratorOptions.cs:line 192
       at OurAppLib.GeneratorOptions.ReadCulturesFromArgs(List`1 arglist, String& errormsg) in c:\AutomatedBuild\projects\1.0\OurApp\OurAppLib\GeneratorOptions.cs:line 358
       at OurAppLib.GeneratorOptions.ReadFromArgs(String[] args, String& errormsg) in c:\AutomatedBuild\projects\1.0\OurApp\OurAppLib\GeneratorOptions.cs:line 261
       at OurApp.Program.Main(String[] args) in c:\AutomatedBuild\projects\1.0\OurApp\OurApp\Program.cs:line 76`print("code sample");`

Answer 1

Found this link, which explains the issue: http://social.msdn.microsoft.com/forums/en-US/asmxandxml/thread/4476f044-bab9-492d-bb94-4e0960bd2d26

A quick summary: When serializing, the object makes a dictionary out of all environment variables, but appears to run a ToLower() on all entries. So, if you have two environment variables that are the same except for casing, you'll get a crash.

This is only going to be a problem when running from inside a system like cygwin which enforces case sensitivity for variables. In our case, we're using make.

There are a couple solutions, but they all revolve around making sure that your environment doesn't have any duplicated variables when your c# app runs.