的NullReferenceException在Microsoft.Silverlight.Build.Tasks.CompileXaml.LoadAssemblies（ITaskItem [] ReferenceAssemblies）

Question

我我的Visual Studio 2010的更新版本10.0.30319.1 RTM版本，並開始在生成過程中收到以下異常：

System.NullReferenceException：未將對象引用設置爲對象的實例。 在Microsoft.Silverlight.Build.Tasks.CompileXaml.LoadAssemblies（ITaskItem [] ReferenceAssemblies） 在Microsoft.Silverlight.Build.Tasks.CompileXaml.get_GetXamlSchemaContext（） 在Microsoft.Silverlight.Build.Tasks.CompileXaml.GenerateCode（ITaskItem項布爾isApplication） 在Microsoft.Silverlight.Build.Tasks.CompileXaml.Execute（） 在Bohr.Silverlight.BuildTasks.BohrCompileXaml.Execute（）

BohrCompileXaml.Execute的代碼如下：

 public override bool Execute() { 
     List<TaskItem> pages = new List<TaskItem>(); 
     foreach (ITaskItem item in SilverlightPages) { 
      string newFileName = getGeneratedName(item.ItemSpec); 
      String content = File.ReadAllText(item.ItemSpec); 
      String parentClassName = getParentClassName(content); 
      if (null != parentClassName) { 
       content = content.Replace("<UserControl", "<" + parentClassName); 
       content = content.Replace("</UserControl>", "</" + parentClassName + ">"); 
       content = content.Replace("bohr:ParentClass=\"" + parentClassName + "\"", ""); 
      } 
      File.WriteAllText(newFileName, content); 
      pages.Add(new TaskItem(newFileName)); 
     } 

     if (null != SilverlightApplications) { 
      foreach (ITaskItem item in SilverlightApplications) { 
       Log.LogMessage(MessageImportance.High, "Application: " + item.ToString()); 
      } 
     } 

     foreach (ITaskItem item in pages) { 
      Log.LogMessage(MessageImportance.High, "newPage: " + item.ToString()); 
     } 


     CompileXaml xamlCompiler = new CompileXaml(); 
     xamlCompiler.AssemblyName = AssemblyName; 
     xamlCompiler.Language = Language; 
     xamlCompiler.LanguageSourceExtension = LanguageSourceExtension; 
     xamlCompiler.OutputPath = OutputPath; 
     xamlCompiler.ProjectPath = ProjectPath; 
     xamlCompiler.RootNamespace = RootNamespace; 
     xamlCompiler.SilverlightApplications = SilverlightApplications; 
     xamlCompiler.SilverlightPages = pages.ToArray(); 
     xamlCompiler.TargetFrameworkDirectory = TargetFrameworkDirectory; 
     xamlCompiler.TargetFrameworkSDKDirectory = TargetFrameworkSDKDirectory; 
     xamlCompiler.BuildEngine = BuildEngine; 
     bool result = xamlCompiler.Execute(); // HERE we got the error! 

而且任務的定義：

 <BohrCompileXaml 
      LanguageSourceExtension="$(DefaultLanguageSourceExtension)" 
      Language="$(Language)" 
      SilverlightPages="@(Page)" 
      SilverlightApplications="@(ApplicationDefinition)" 
      ProjectPath="$(MSBuildProjectFullPath)" 
      RootNamespace="$(RootNamespace)" 
      AssemblyName="$(AssemblyName)" 
      OutputPath="$(IntermediateOutputPath)" 
      TargetFrameworkDirectory="$(TargetFrameworkDirectory)" 
      TargetFrameworkSDKDirectory="$(TargetFrameworkSDKDirectory)" 
      > 

     <Output ItemName="Compile" TaskParameter="GeneratedCodeFiles" /> 

     <!-- Add to the list list of files written. It is used in Microsoft.Common.Targets to clean up 
      for a next clean build 
      --> 
     <Output ItemName="FileWrites" TaskParameter="WrittenFiles" /> 
     <Output ItemName="_GeneratedCodeFiles" TaskParameter="GeneratedCodeFiles" /> 

    </BohrCompileXaml> 

可能是什麼原因？我怎樣才能獲得更多信息CompileXaml類中發生了什麼？

Answer 1

我的第一個猜測是參數ReferenceAssemblies爲空。 ReferenceAssemblies用於獲得CompileTask中的XamlSchemaContext。

要使其工作，你有兩個選擇：

• 設置屬性SkipLoadingAssembliesInXamlCompiler到true
• 或者在ReferenceAssemblies屬性傳遞一個裝配路徑（mscorlib.dll中或其他Silverlight的DLL）

更簡單的是將屬性SkipLoadingAssembliesInXamlCompiler設置爲true。要做到這一點修改BohrCompileXaml任務那樣：

CompileXaml xamlCompiler = new CompileXaml(); 
... 
xamlCompiler.SkipLoadingAssembliesInXamlCompiler = true;