MSB0001: Internal MSBuild Error: Task Instance should be null

Question

So I've recently began to with the MSBUILD api for framework 4.0. Whenever I try to build my solution, one of my projects returns a failure in the OverallResult Failure Microsoft.Build.Execution.BuildResultCode. Only 1 project fails, all the rest build successfully. Buried way down is the exception - MSB0001: Internal MSBuild Error: Task Instance should be null. Here's the stack:

StackTrace  "   at Microsoft.Build.Shared.ErrorUtilities.ThrowInternalError(String message, Exception innerException, Object[] args)\r\n   at Microsoft.Build.Shared.ErrorUtilities.VerifyThrow(Boolean condition, String unformattedMessage)\r\n   at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.CleanupForTask()\r\n   at Microsoft.Build.BackEnd.TaskBuilder.<ExecuteTask>d__5.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n   at Microsoft.Build.BackEnd.TaskBuilder.<ExecuteTask>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n   at Microsoft.Build.BackEnd.TargetEntry.<ProcessBucket>d__16.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n   at Microsoft.Build.BackEnd.TargetEntry.<ExecuteTarget>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter.GetResult()\r\n   at Microsoft.Build.BackEnd.TargetBuilder.<ProcessTargetStack>d__1b.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter.GetResult()\r\n   at Microsoft.Build.BackEnd.TargetBuilder.<BuildTargets>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n   at Microsoft.Build.BackEnd.RequestBuilder.<BuildProject>d__26.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n   at Microsoft.Build.BackEnd.RequestBuilder.<BuildAndReport>d__16.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter.GetResult()\r\n   at Microsoft.Build.BackEnd.RequestBuilder.<RequestThreadProc>d__12.MoveNext()"   string

When I build using the dev engine for Visual Studio or the commandline - it works fine, no errors. I'm really confused about what's causing this. Would love some insight.

Ali Hamadi Ali Hamadi · Accepted Answer · 2016-02-08T16:19:59

I believe that you have implemented the ITask interface, without getting rid of the throw exceptions. all you need to do is to set methods this way:

 public IBuildEngine BuildEngine
    { get; set; }

    public ITaskHost HostObject
    { get; set; }

MSB0001: Internal MSBuild Error: Task Instance should be null

1 Answers