I'm trying to convert code from a WFA (Windows Form Application) over to a WPF. However, i'm running into many difficulties. There is no .MaxLength. There is also no .Text as there is when using a Windows Form Application. How would i re-write the following code for WPF? 

xbox is refering to a box on a chat window where the user types in text.... 

PS. The code below DOES work for WFA.... 

```
private void BoxChatAreaKeyPress(object sender, KeyPressEventArgs e)
{
    var xBox = (RichTextBox) sender;

    //setting a limit so the user cannot type more than 4000 characters at once
    xBox.MaxLength = 4000;
    if ((xBox.Text.Length > 1) && (e.KeyChar == (char) Keys.Enter))
    {
        WriteMessage(xBox);
    }
}

private static void WriteMessage(RichTextBox xBox)
{
    var writer = new StreamWriter(_client.GetStream());
    String message = xBox.Text.TrimEnd('\n') + "|" + _font.Name;
    writer.WriteLine(message);
    writer.Flush();
    xBox.Text = null;
}

```