How do I create an Autoscrolling TextBox

Question

I have a WPF application that contains a multiline TextBox that is being used to display debugging text output.

How can I set the TextBox so that as text is appended to

Answer 1

The problem with the "ScrollToEnd" method is that the TextBox has to be visible, or it won't scroll.

Therefore a better method is to set the TextBox Selection property to end of document:

  static void tb_TextChanged(object sender, TextChangedEventArgs e)
  {
     TextBox tb = sender as TextBox;
     if (tb == null)
     {
        return;
     }

     // set selection to end of document
     tb.SelectionStart = int.MaxValue;
     tb.SelectionLength = 0;         
  }

BTW, the memory leak handling in the first example is likely unnecessary. The TextBox is the publisher and the static Attached Property event handler is the subscriber. The publisher keeps a reference to the subscriber which can keep the subscriber alive (not the other way around.) So if a TextBox goes out of scope, so will the reference to the static event handler (i.e., no memory leak.)

So hooking up the Attached Property can be handled simpler:

  static void OnAutoTextScrollChanged
      (DependencyObject obj, DependencyPropertyChangedEventArgs args)
  {
     TextBox tb = obj as TextBox;
     if (tb == null)
     {
        return;
     }

     bool b = (bool)args.NewValue;

     if (b)
     {
        tb.TextChanged += tb_TextChanged;
     }
     else
     {
        tb.TextChanged -= tb_TextChanged;
     }
  }