Question

I updated my Visual Studio 2010 to the version 10.0.30319.1 RTM Rel and start getting the following exception during the build:

System.NullReferenceException: Object reference not set to an instance of an object.
at Microsoft.Silverlight.Build.Tasks.CompileXaml.LoadAssemblies(ITaskItem[] ReferenceAssemblies)
at Microsoft.Silverlight.Build.Tasks.CompileXaml.get_GetXamlSchemaContext()
at Microsoft.Silverlight.Build.Tasks.CompileXaml.GenerateCode(ITaskItem item, Boolean isApplication)
at Microsoft.Silverlight.Build.Tasks.CompileXaml.Execute()
at Bohr.Silverlight.BuildTasks.BohrCompileXaml.Execute()

The code of BohrCompileXaml.Execute is the following:

     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!  

And the definition of the task:

        <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>

What can be the reason? And how can I get more info what’s happening inside CompileXaml class?

Answer 1

My first guess is that the parameter ReferenceAssemblies is null. ReferenceAssemblies is used to get the XamlSchemaContext in CompileTask.

To make it work, you have two choice :

• Set the property SkipLoadingAssembliesInXamlCompiler to true
• Or pass an assembly path in ReferenceAssemblies property (mscorlib.dll or another silverlight dll)

The simpler is to set the property SkipLoadingAssembliesInXamlCompiler to true. To do that modify your BohrCompileXaml task like that :

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