无法更改 TextBox 文本

Question

我想在我的 Backgroundworker 中更改 TextBox 的文本，但它不起作用，而且我在我的代码中找不到错误。

后台工作者：

class Check_Server
{
    WebSocket webSocket = new WebSocket("ws://localhost:8548");
    private Form1 Form1;

    public void Check_WebSocket(object sender, DoWorkEventArgs e)
    {
        BackgroundWorker worker = sender as BackgroundWorker;
        while (!worker.CancellationPending)
        {
            Console.WriteLine("checking connection");
            if (webSocket.IsAlive == true)
            {
                Console.WriteLine("connected");
            }
            else
            {
                Console.WriteLine("not connected");
                
                Form1 form = new Form1();
                form.SetText("XYZ");
                MakeNewConnection();
            }
        }
    }

    void MakeNewConnection()
    {
        webSocket.Connect();      
        Thread.Sleep(10000);
    } 
}

表格：

public void SetText(string text)
{
    if (InvokeRequired)
    {
        this.Invoke((MethodInvoker)delegate () { SetText(text); });
        return;
    }
    
    textBox1.Text += text;
}

Answer 1

您没有显示您的表单。添加 form.Show() 或 form.ShowDialog()，具体取决于您是否要等到用户关闭表单。

此外，我发现此扩展方法对于对控件进行线程安全更改非常有用。像这样使用它：textBox1.InvokeSave(() => textBox1.Text += text);.

public static partial class ControlExtensions
{
    public static void InvokeSave(this Control control, Action action)
    {
        Delegate del = action;

        try
        {
            if (control.InvokeRequired)
            {
                control.Invoke(del);
            }
            else action();
        }
        catch (ObjectDisposedException)
        {
            // guess do nothing is fine then
        }
    }
}

Answer 2

使用来自 Mariusz Kotas 的库使 winforms 中的 Websockets 变得容易得多，也许并不奇怪，Websocket.Client；如果你打开 VS 的 nuget 包管理器并搜索它，你会找到它（目前大约是 4.3 版）

设置可能如下所示：

private WebsocketClient _cws;

private async void ConnectButton_Click(..){

    _cws = new WebsocketClient(new Uri("your uri here"));

    _cws.MessageReceived.Subscribe(msg => MessageReceived(msg.Text));

    _cws.DisconnectionHappened.Subscribe(info => DoSomething("Disconnection happened: " + info));
}

发送消息可能如下所示：

private async void ConnectButton_Click(..){
    _cws.Send(messageTextBox.Text);
}

收到以上订阅的消息：

private void MessageReceived(string msg)

    //local function for logging
    void addAndScrollAsync()
    {
        _messagesListBox.Items.Add( msg);

        //this scrolls to show new messages while the listbox is at the bottom, but doesn't if it's been scrolled up
        int visibleItems = _messagesListBox.ClientSize.Height / _messagesListBox.ItemHeight;
        if (_messagesListBox.Items.Count > visibleItems && _messagesListBox.TopIndex > _messagesListBox.Items.Count - visibleItems - 2)
            _messagesListBox.TopIndex = _messagesListBox.Items.Count - visibleItems + 1;

    }

    _messagesListBox.InvokeEx(() => addAndScrollAsync());
        

}

我有一些辅助扩展来执行任何调用：

public static class ControlExtensions
{
    public static TResult InvokeEx<TControl, TResult>(this TControl control,
                                               Func<TControl, TResult> func)
      where TControl : Control
    {
        return control.InvokeRequired
                ? (TResult)control.Invoke(func, control)
                : func(control);
    }

    public static void InvokeEx<TControl>(this TControl control,
                                          Action<TControl> func)
      where TControl : Control
    {
        control.InvokeEx(c => { func(c); return c; });
    }

    public static void InvokeEx<TControl>(this TControl control, Action action)
      where TControl : Control
    {
        control.InvokeEx(c => action());
    }
}

无法更改 TextBox 文本

Can't change the TextBox text

c#

winforms