Question

我有一个ContextMenuStrip控件，允许您执行两种不同的操作：Sync和Async。

我试图用泛型来覆盖所有内容，所以我这样做了：

public class BaseContextMenu<T> : IContextMenu
{
   private T executor;

   public void Exec(Action<T> action)
   {
      action.Invoke(this.executor);
   }

   public void ExecAsync(Action<T> asyncAction)
   {
       // ...
   }

如何编写异步方法以执行通用操作并同时使用菜单“执行某些操作”？我看到BeginInvoke的签名是这样的：

asyncAction.BeginInvoke(this.executor, IAsyncCallback, object);

Answer 1

这是Jeffrey Richter关于.NET异步编程模型的文章。 http://msdn.microsoft.com/en-us/magazine/cc163467.aspx

以下是如何使用BeginInvoke的示例：

public class BaseContextMenu<T> : IContextMenu
{
    private T executor;

    public void Exec(Action<T> action)
    {
        action.Invoke(this.executor);
    }

    public void ExecAsync(Action<T> asyncAction, AsyncCallback callback)
    {
        asyncAction.BeginInvoke(this.executor, callback, asyncAction);
    }
}

这是一个可以传递给ExecAsync的回调方法：

private void Callback(IAsyncResult asyncResult)
{
    Action<T> asyncAction = (Action<T>) asyncResult.AsyncState;
    asyncAction.EndInvoke(asyncResult);
}

Answer 2

最简单的选择：

// need this for the AsyncResult class below
using System.Runtime.Remoting.Messaging;

public class BaseContextMenu<T> : IContextMenu
{
    private T executor;

    public void Exec(Action<T> action) {
        action.Invoke(this.executor);
    }

    public void ExecAsync(Action<T> asyncAction) {
        // specify what method to call when asyncAction completes
        asyncAction.BeginInvoke(this.executor, ExecAsyncCallback, null);
    }

    // this method gets called at the end of the asynchronous action
    private void ExecAsyncCallback(IAsyncResult result) {
        var asyncResult = result as AsyncResult;
        if (asyncResult != null) {
            var d = asyncResult.AsyncDelegate as Action<T>;
            if (d != null)
                // all calls to BeginInvoke must be matched with calls to
                // EndInvoke according to the MSDN documentation
                d.EndInvoke(result);
        }
    }
}

Action T同步和异步

2 个答案: