Question

我是C＃的新手，我想使用线程编写一个聊天程序，其中每一侧有两个线程（一个用于监听，另一个用于发送消息）。

但是，线程无法使用组件（即Textbox），因为另一个线程已经捕获了它。

这是我的代码：

服务器端：

private TcpClient clientSocket;

private void btnStartListening_Click(object sender, EventArgs e)
{
    TcpListener serverSocket = new TcpListener(int.Parse(txtPort.Text));
    int requestCount = 0;
    clientSocket = default(TcpClient);
    serverSocket.Start();
    txtReceivedMessages.Text +=" >> Server Started\n";
    clientSocket = serverSocket.AcceptTcpClient();
    txtReceivedMessages.Text += " >> Accept connection from client\n";
    requestCount = 0;
    Thread t = new Thread(listeningThread);          
    t.Start();      
    clientSocket.Close();
    serverSocket.Stop();                    
}

private void listeningThread()
{
    while (true)
    {
        try
        {                  
            NetworkStream networkStream = clientSocket.GetStream();
            byte[] bytesFrom = new byte[10025];
            networkStream.Read(bytesFrom, 0, (int)clientSocket.ReceiveBufferSize);
            string dataFromClient = System.Text.Encoding.ASCII.GetString(bytesFrom);
            dataFromClient = dataFromClient.Substring(0, dataFromClient.IndexOf("$"));                
            string serverResponse = "Last Message from client" + dataFromClient;                
            networkStream.Flush();                
            txtReceivedMessages.Text += dataFromClient;
            txtReceivedMessages.Update();
        }
        catch (Exception ex)
        {
            txtReceivedMessages.Text += ex.ToString() + "\n";
        }
    }
}

private void btnSend_Click(object sender, EventArgs e)
{
    NetworkStream networkStream = clientSocket.GetStream();
    Byte[] data = Encoding.ASCII.GetBytes(txtSendMessage.Text);
    networkStream.Write(data, 0, data.Length);
}

客户方：

private NetworkStream serverStream;
private void btnSend_Click(object sender, EventArgs e)
{
    serverStream = clientSocket.GetStream();
    byte[] outStream = System.Text.Encoding.ASCII.GetBytes(txtMsgToSend.Text + "$");
    serverStream.Write(outStream, 0, outStream.Length);
    serverStream.Flush();


}

private void listeningThread()
{
    byte[] inStream = new byte[10025];
        serverStream.Read(inStream, 0, (int)clientSocket.ReceiveBufferSize);
        string returndata = System.Text.Encoding.ASCII.GetString(inStream);
        txtReceivedMsgs.Text += ">>" + returndata;
        txtMsgToSend.Text = "";
        txtMsgToSend.Focus();
}

private void btnSetConfiguration_Click(object sender, EventArgs e)
{
    txtReceivedMsgs.Text += "Client Started";
    clientSocket.Connect(txtIP.Text, int.Parse(txtPort.Text));
    lblStatus.Text = "Client Socket Program - Server Connected ...";
}

Answer 1

如果要从另一个线程更新表单控件，则需要使用Invoke（）方法。

从SO上的这篇文章中查看更多内容 How to update the GUI from another thread in C#?

修改：来自关联帖子的内容

对于.NET 2.0，这里有一些我编写的代码，它可以完全满足您的需求，适用于Control上的任何属性：

private delegate void SetControlPropertyThreadSafeDelegate(
                         Control control, 
                         string propertyName, 
                         object propertyValue);

public static void SetControlPropertyThreadSafe(
                         Control control, 
                         string propertyName, 
                         object propertyValue)
{
  if (control.InvokeRequired)
  {
    control.Invoke(new SetControlPropertyThreadSafeDelegate               
    (SetControlPropertyThreadSafe), 
    new object[] { control, propertyName, propertyValue });
  }
  else
  {
    control.GetType().InvokeMember(
    propertyName, 
    BindingFlags.SetProperty, 
    null, 
    control, 
    new object[] { propertyValue });
  }
}

这样称呼：

// thread-safe equivalent of
// myLabel.Text = status;
SetControlPropertyThreadSafe(myLabel, "Text", status);

如果您使用的是.NET 3.0或更高版本，则可以将上述方法重写为Control类的扩展方法，这样可以简化对以下内容的调用：

myLabel.SetPropertyThreadSafe("Text", status);

更新05/10/2010：

对于.NET 3.0，您应该使用以下代码：

private delegate void SetPropertyThreadSafeDelegate<TResult>(
                          Control @this, 
                          Expression<Func<TResult>> property, 
                          TResult value);

public static void SetPropertyThreadSafe<TResult>(
                          this Control @this, 
                          Expression<Func<TResult>> property, 
                          TResult value)
{
  var propertyInfo = (property.Body as MemberExpression).Member 
  as PropertyInfo;

  if (propertyInfo == null ||
      !@this.GetType().IsSubclassOf(propertyInfo.ReflectedType) ||
      @this.GetType().GetProperty(
      propertyInfo.Name, 
      propertyInfo.PropertyType) == null)
  {
    throw new ArgumentException("The lambda expression 'property' must      reference a valid property on this Control.");
  }

  if (@this.InvokeRequired)
  {
  @this.Invoke(new SetPropertyThreadSafeDelegate<TResult> 
  (SetPropertyThreadSafe), 
  new object[] { @this, property, value });
  }
  else
  {
      @this.GetType().InvokeMember(
      propertyInfo.Name, 
      BindingFlags.SetProperty, 
      null, 
      @this, 
      new object[] { value });
  }
}

使用LINQ和lambda表达式来允许更清晰，更简单和更安全的语法：

myLabel.SetPropertyThreadSafe(() => myLabel.Text, status); // status has to be a string or this will fail to compile

现在不仅在编译时检查属性名称，属性的类型也是如此，因此不可能（例如）将字符串值赋给布尔属性，因此导致运行时异常。

不幸的是，这并不能阻止任何人做一些愚蠢的事情，例如传递另一个Control的属性和值，所以以下内容将很乐意编译：

myLabel.SetPropertyThreadSafe(() => aForm.ShowIcon, false);

因此，我添加了运行时检查，以确保传入的属性确实属于调用该方法的Control。不完美，但仍然比.NET 2.0版本好很多。

如果有人对如何为编译时安全性改进此代码有任何进一步的建议，请发表评论！

Windows表单聊天应用程序使用线程

1 个答案: