Question

从未尝试使用Windows窗体进行异步调用。我不能使用新的aynch/await，因为我不拥有最近的Visual Studio / .NET。我需要的是＆＃34;执行一个请求很长时间的操作（填充IList）＆＃34;并且，当它完成后，在TextBox上写下该列表的结果。

在互联网上搜索我发现这个例子似乎有用，但TOO在我看来符合（也许有些事情快速而简单）：

private void button1_Click(object sender, EventArgs e)
{
    MyTaskAsync();
}

private void MyTaskWorker()
{
    // here I populate the list. I emulate this with a sleep of 3 seconds
    Thread.Sleep(3000);
}

private delegate void MyTaskWorkerDelegate();

public void MyTaskAsync()
{
    MyTaskWorkerDelegate worker = new MyTaskWorkerDelegate(MyTaskWorker);
    AsyncCallback completedCallback = new AsyncCallback(MyTaskCompletedCallback);

    AsyncOperation async = AsyncOperationManager.CreateOperation(null);
    worker.BeginInvoke(completedCallback, async);
}

private void MyTaskCompletedCallback(IAsyncResult ar)
{
    MyTaskWorkerDelegate worker = (MyTaskWorkerDelegate)((AsyncResult)ar).AsyncDelegate;
    AsyncOperation async = (AsyncOperation)ar.AsyncState;

    worker.EndInvoke(ar);

    AsyncCompletedEventArgs completedArgs = new AsyncCompletedEventArgs(null, false, null);
    async.PostOperationCompleted(delegate(object e) { OnMyTaskCompleted((AsyncCompletedEventArgs)e); }, completedArgs);
}

public event AsyncCompletedEventHandler MyTaskCompleted;

protected virtual void OnMyTaskCompleted(AsyncCompletedEventArgs e)
{
    if (MyTaskCompleted != null)
        MyTaskCompleted(this, e);

    // here I'll populate the textbox
    textBox1.Text = "... content of the Iteration on the List...";
}

对于这种简单的操作，我真的需要像50行代码这样的东西吗？或者我可以删除一些东西？完成后我只需要一个简单的异步调用 - ＆gt;回调。

没有锁，根本没有并发......

Answer 1

您可以将CPL与C＃4.0一起使用，如下所示：

private void button1_Click(object sender, EventArgs e)
{
    Task.Factory.StartNew(() => DoWork())
        .ContinueWith(t => UpdateUIWithResults(t.Result)
        , CancellationToken.None
        , TaskContinuationOptions.None
        , TaskScheduler.FromCurrentSynchronizationContext());
}

这在线程池线程中启动DoWork，允许它从UI线程中进行处理，然后在UI线程中运行UpdateUIWithResults，并将结果传递给DoWork。

Answer 2

您可以使用Task.Factory.StartNew将工作推送到线程池。 Task.ContinueWith会给你一个“完成的回调”。

private void button1_Click(object sender, EventArgs e)
{
    var ui = TaskScheduler.FromCurrentSynchronizationContext();
    Task<List<T>> task = Task.Factory.StartNew(() => MyTaskWorker());
    task.ContinueWith(t => OnMyTaskCompleted(t), ui);
}

private List<T> MyTaskWorker()
{
    // here I populate the list. I emulate this with a sleep of 3 seconds
    Thread.Sleep(3000);
    return ...;
}

protected virtual void OnMyTaskCompleted(Task t)
{
    // here I'll populate the textbox with t.Result
    textBox1.Text = "... content of the Iteration on the List...";
}

第一个实验调用异步方法 - 我是否需要所有这些代码？

2 个答案: