Error :The "ValidateXaml" task Failed unexpectedly.
System.NullReferenceException: Object reference not set to an instance of an object.
at MS.MarkupCompiler.ValidationPass.ValidateXaml(String fileName,Assembly[] assemblies,Assembly callingAssembly,TaskLoggingHelper log,Boolean shouldThrow)
at Microsoft.Silverlight.Build.Tasks.ValidateXaml.XamlValidator.Execute(ITask task)
at Microsoft.Silverlight.Build.Tasks.ValidateXaml.XamlValidator.Execute(ITask task)
at Microsoft.Silverlight.Build.Tasks.ValidateXaml.Execute()
at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute()
at Microsoft.Build.BackEnd.TaskBuilder.ExecuteInstantiatedTask(ITaskExecutionHost taskExecutionHost,TaskLoggingContext taskLoggingContext,TaskHost taskHost,ItemBucket bucket,TaskExecutionMode howToExecuteTask,Boolean& taskResult)

解决方法:设置. vbproj文件中 <ValidateXaml>false</ValidateXaml>