如何从BeginInvoke返回T值？

问题描述

我想编写一个类来简化异步编程，例如字符串s = mylib.BeginInvoek（test， 1）;这是我的代码：

I want to write a class to simplify the asynchronous programing, like string s = mylib.BeginInvoek(test,"1"); here is my code:

   public T BeginInvokeExWithReturnValue<T>(Func<T> actionFunction)
    {
        ExecWithReturnType<T> execWtihReturnValue = new ExecWithReturnType<T>(actionFunction);
        IAsyncResult iar = execWtihReturnValue.BeginInvoke(new AsyncCallback(EndInvokeExWithReturnValue<T>), execWtihReturnValue);
        // how to code here to return value
    }

    private void EndInvokeExWithReturnValue<T>(IAsyncResult iar)
    {
        ExecWithReturnType<T> execWtihReturnValue = (ExecWithReturnType<T>)iar.AsyncState;
        execWtihReturnValue.EndInvoke(iar);
    }

此BeginInvokeExWithReturnValue函数没有输入参数，但返回值
但是我不知道如何从BeginInvokeExWithReturnValue函数返回值。任何人都知道吗，您能帮我吗？

this BeginInvokeExWithReturnValue function has no input parameter, but returns a value,But I don't know how to return a value from BeginInvokeExWithReturnValue function. Anyone who know this, Could you pls help me ? thx very much.

推荐答案

您现在试图做的事情不是异步的。如果您想返回 T ，只需使用：

What you are trying to do right now is not async; if you want to return the T, just use:

return actionFunction();

这会减少开销。

如果您希望异步，并且您使用的是4.0，那么TPL可能是一个不错的选择：

If you want async, and you are on 4.0, then the TPL may be a good option:

public Task<T> BeginInvokeExWithReturnValue<T>(Func<T> actionFunction)
{
    var task = new Task<T>(actionFunction);
    task.Start();
    return task;
}

现在，呼叫者可以使用：

Now the caller can use:

var task = BeginInvokeExWithReturnValue(() => Whatever());

然后在需要时检查是否完成，阻止（等待

and then when desired, check for completion, block (Wait) for completion, register continuations, etc. Or just:

var result = task.Result; // implicit wait
Console.WriteLine(result);

这可让您无缝编写异步代码。或在C＃5.0中，无缝编写延续：

This allows you to seamlessly write async code. Or in C# 5.0, seamlessly write continuations:

var result = await task; // continuation - this is **not** a wait
Console.WriteLine(result);

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