c# - 除非明确定义，否则System.Action在单元测试中不知道

Question

我遇到了一个奇怪的问题，即System.Action在上面未明确定义时无法解决。为了更好地解释这一点，我向您展示了代码

    [TestMethod]
    public void Channel_Dispatch_Waits_Before_Return()
    {
        //Action useless = null;

        WorkflowChannel channel = new WorkflowChannel();
        bool isHandeled = false;

        channel.Subscribe(WorkflowHandlerFactory.FromLambdaAsync<int>((data, callback, onError) =>
        {
            // Go on another thread and sleep for a small ammount of time to simulate a async request
            System.Threading.ThreadPool.QueueUserWorkItem(state =>
            {
                System.Threading.Thread.Sleep(100);

                isHandeled = true;

                callback();
            });
        }));


        channel.Dispatch(1);

        Assert.IsTrue(isHandeled);
    }

这给出了编译时错误，即:

Error 1 Delegate 'Action' does not take 0 arguments C:\Users***\Documents\Visual Studio 2010\Projects\MessageWorkflow\MessageWorkfow.Test\WorkflowChannelTest.cs 47 21 MessageWorkflow.Test

但是，当我取消注释该行时:

Action useless = null;

它不会给出编译时错误。我试图重建等，但没有用。
如果需要，FromLambdaAsync的声明为:

public static IWorkflowHandler FromLambdaAsync<T>(AsyncAction<T> method)

其中AsyncAction是:

public delegate void AsyncAction<T>(T message, Action onComplete, Action<Exception> onError);

它不是一帆风顺的，但我很困惑，因为我在这背后找不到任何逻辑……谁能打我一巴掌？

干杯!

*编辑*

我设法在最简单的测试用例中重现了此行为，请参见:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ClassLibrary2
{
    public delegate void AsyncAction(Action onComplete);

    public class WorkflowHandler
    {

    }

    public class Main
    {
        public static WorkflowHandler FromLambdaAsync(AsyncAction method)
        {
            return new WorkflowHandler();
        }
    }
}

与单元测试:

using ClassLibrary2;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System;

namespace TestProject1
{
    [TestClass]
    public class MainTest
    {
        [TestMethod()]
        public void FromLambdaAsyncTest()
        {
            Main.FromLambdaAsync((callback) =>
                {
                    callback();
                });
        }
    }
}

这给了我同样的错误

该项目针对.NET 4.0 usign VS 2010 sp1进行编译

*编辑2:*

进一步简化了测试用例，结果没有变化

*编辑3 *

即使在最简单的测试用例中，此操作也会失败，请参见:

[TestMethod()]
public void FromLambdaAsyncTest()
{
    AsyncAction action = c => c();
}

Answer 1

重复:请参阅'Delegate 'System.Action' does not take 0 arguments.' Is this a C# compiler bug (lambdas + two projects)?