Action T同步和異步

Question

我有一個ContextMenuStrip控件，允許您執行一個動作是兩種不同的風格： Sync和Async 。

我試圖用泛型覆蓋所有內容所以我這樣做：

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

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

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

我如何編寫異步方法以執行通用操作並同時使用菜單“執行某些操作”？ 我看到BeginInvoke的簽名是這樣的：

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

Answer 1

這是Jeffrey Richter關於.NET異步編程模型的文章。 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);
    }
}

這是一個可以傳遞給ExecAsync的回調方法：

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

Answer 2

最簡單的選擇：

// 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);
        }
    }
}