Question

我有这段代码：

private void buttonStart_Click(object sender, EventArgs e)
{
    Task.Factory.StartNew(() => GeneraListaCartelle())
        .ContinueWith(t => GeneraListaCartelleCompletata()
        , CancellationToken.None
        , TaskContinuationOptions.None
        , TaskScheduler.FromCurrentSynchronizationContext());
}

private void GeneraListaCartelle()
{
    try
    {
        ... some operation ....
    }
    catch (Exception err)
    {
        txtErrors.AppendText(err.Message);
    }
}

GeneraListaCartelleCompletata()
{
    ... process finished...
}

和txtErrors位于“主”线程（UI）中。当我发现错误时，异步线程无法写入UI控件，我得到invalid cross-thread exception。

我可以在线程内与UI对话吗？

Answer 1

如果您使用的是WinForms，则需要在UI线程上调用您的方法，如

catch (Exception err)
{
    if(this.InvokeRequired){
        Action<Exception> act = ((ex) => {
            txtErrors.AppendText(ex.Message);
        }); 
        this.Invoke(act, new object[] { err });
    }
    else{
        txtErrors.AppendText(err.Message);
    }
}

如果您使用的是WPF，则需要

catch (Exception err)
{
    if(this.Dispatcher.CheckAccess()){
       txtErrors.AppendText(err.Message);
    }
    else {
           Action<Exception> act = ((ex) => {
            txtErrors.AppendText(ex.Message);
           }); 
        this.Dispatcher.Invoke(act, new object[] { err });
    }
}

Answer 2

如果您的目标是WinForm应用程序，那么：

try
    {
        ... some operation ....
    }
catch (Exception err)
    {
       if (txtErrors.InvokeRequired)
        {
            txtErrors.BeginInvoke(new MethodInvoker(
                delegate { txtErrors.AppendText(err.Message); })
                );
        }
    }

Answer 3

msdn有一个例子：

// This delegate enables asynchronous calls for setting
// the text property on a TextBox control.
delegate void SetTextCallback(string text);

// This method demonstrates a pattern for making thread-safe
// calls on a Windows Forms control. 
//
// If the calling thread is different from the thread that
// created the TextBox control, this method creates a
// SetTextCallback and calls itself asynchronously using the
// Invoke method.
//
// If the calling thread is the same as the thread that created
// the TextBox control, the Text property is set directly.
private void SetText(string text)
{
    // InvokeRequired required compares the thread ID of the
    // calling thread to the thread ID of the creating thread.
    // If these threads are different, it returns true.
    if (this.textBox1.InvokeRequired)
    {
        SetTextCallback d = new SetTextCallback(SetText);
        this.Invoke(d, new object[] { text });
    }
    else
    {
        this.textBox1.Text = text;
    }
}

Answer 4

在调用的form_load事件处理程序中将CheckForIllegalCrossThreadCalls设置为false

Answer 5

从一个旧项目中拉出来，我不得不处理从另一个线程更新UI的问题。也应该适合你。

delegate void addtoValProg();
addtoValProg myDelegate;

myDelegate = new addtoValProg(invokeControl);

private void GeneraListaCartelle()
{
    try
    {
        //... some operation ....
    }
    catch (Exception err)
    {
        invokeControl();
    }
}

private void invokeControl()
{
    if (this.InvokeRequired)
    {
        this.Invoke(this.myDelegate);
    }
    else
    {
        txtErrors.AppendText(err.Message);
        txtErrors.Update();
    }
}

与UI交谈的话题？

5 个答案: