如何创建立即完成的IAsyncResult？

Question

我正在实现一个需要实现BeginDoSomething和EndDoSomething方法的接口.然而,我DoSomething并不是真的长期奔跑.为简单起见,假设DoSomething只比较两个变量并返回是否a> b

所以我的BeginDoSomething应该是这样的:

protected override IAsyncResult BeginDoSomething(int a, int b, AsyncCallback callback, object state)
{
     bool returnValue = a > b;
     return ...; //what should I return here?  
     //The method actually already completed and I don't need to wait for anything
 }

我不知道应该归还什么.我只是实现,BeginDoSomething因为我必须,而不是因为我的方法是长期运行.我需要实现自己的IAsyncResult吗？.NET库中是否已有实现？

Answer 1

这有点快速和脏,但您可以实现一个实现IAsyncResult的类,如下所示:

    public class MyAsyncResult : IAsyncResult
    {
        bool _result;

        public MyAsyncResult(bool result)
        {
            _result = result;
        }

        public bool IsCompleted
        {
            get { return true; }
        }

        public WaitHandle AsyncWaitHandle
        {
            get { throw new NotImplementedException(); }
        }

        public object AsyncState
        {
            get { return _result; }
        }

        public bool CompletedSynchronously
        {
            get { return true; }
        }
    }

然后在你的BeginDoSomething中使用它:

    return new MyAsyncResult(a > b);

Answer 2

快速入侵的方法是使用委托:

protected override IAsyncResult BeginDoSomething(int a, int b, AsyncCallback callback, object state)
{
     bool returnValue = a > b;
     Func<int,int,bool> func = (x,y) => x > y;
     return func.BeginInvoke(a,b,callback,state);
}

这种方法的缺点是,如果两个线程同时调用此方法,则需要小心,否则会出错.