accessing delegate from another class which points to a method?

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C#

C#4.0

Using VS2010, I am busy writing a chat application. In my class "Connection", I have a method which reads the receiving messages. In my "form's" code, I have a method that updates the textbox (which is multi line) with the newest message received. How do I go about using a delegate to point to the "AppendTextBox" when the "ReadMessage" method within the connection class is done reading?

Here is some of my code:

Class Connection
{
        private void ReadMessages()
        {
            NetworkStream stream = tcpClient.GetStream();

            if (stream.CanRead)
            {
                byte[] bytesToRead = new byte[1024];
                StringBuilder completeMessage = new StringBuilder();

                int numberOfBytesToRead = 0;

                numberOfBytesToRead = stream.Read(bytesToRead, 0,     bytesToRead.Length);

                completeMessage.AppendFormat("{0}", Encoding.ASCII.GetString(bytesToRead, 0, numberOfBytesToRead));

                
            }
        }
}

Namespace Whatever
{
   public delegate void _UpdateMyTextBox(string message);

   public partial class Form1
   {
       public void AppendTextBox(string message)
        {
            txtMessages.AppendText(message + "\r\n");
        }

   }
}