异常“类型'System.Object []'的对象不能转换为类型”

Question

I'm a newbie for C#. I have a problem while updating textbox in WPF from thread that running in another class.

My exception is:

Object of type 'System.Object[]' cannot be converted to type

Here is my code in form:

public void UpdateUserOnline(userOnlineClass message)
{
    if(onLineTextbox.Dispatcher.CheckAccess())
    {
         // The calling thread owns the dispatcher, and hence the UI element
         for (int i = 0; i < message.user.Length; i++)
         {
            // this.Dispatcher.Invoke(Action)
            onLineTextbox.AppendText("•" + message.user + "\r\n");
            onLineTextbox.AppendText(" ->" + message.status + "\r\n");
            // txtDestination.Items.Add(message.user[i]);
        }
    }
    else
    {
        // Invokation required
        onLineTextbox.Dispatcher.Invoke(DispatcherPriority.Normal,new UpdateUserOnlineCallback(UpdateUserOnline), new Object[] { message } );
    }
}

And this is my part of code from my Thread class:

thrMessaging = new Thread(new ThreadStart(ReceiveMessages));
thrMessaging.Start();

private void ReceiveMessages()
{
    Response = null;

    while (chatClient.Connected)
    {
        if (strm.DataAvailable)
        {
            Response = (commandClass)reciveFormatter.Deserialize(strm);

            processMessage(Response);
            //procProcessMessageCallback(processMessage), new object[] { Response });
            //ProcessMessageCallback proccess = new ProcessMessageCallback(processMessage(Response));      
        }
    }
}    

private void processMessage(commandClass message)
{
    /*
    if (message.money != null)
    {
        UpdateUserRanking((userRankingClass)message.money);
    }
    */
    if (message.online != null)
    {
        waitinglist.UpdateUserOnline((userOnlineClass)message.online);
    }
}

Answer 1

onLineTextbox.Dispatcher.Invoke(
    DispatcherPriority.Normal,
    new UpdateUserOnlineCallback(UpdateUserOnline),
    new Object[] { message } );

You're using the wrong overload method.

You're using invoke(priority,delegate,object) - but with an object array.

if you want to pass an object array - swap your priority and delegate around, like so:

onLineTextbox.Dispatcher.Invoke(
    new UpdateUserOnlineCallback(UpdateUserOnline),
    DispatcherPriority.Normal,
    new Object[] { message } );

The overload you're using is expecting an Object, rather than Object[]

Source: http://msdn.microsoft.com/en-us/library/ms591596.aspx and http://msdn.microsoft.com/en-us/library/cc647499.aspx

Answer 2

The Dispatcher.Invoke overloads are a bit strange. There is a single argument overload, and a multiple argument overload that takes the first argument in a separate parameter from the params array of remaining arguments. Use "message" as the third argument without wrapping it in an array.