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

Hmm this seemed like an interesting thing to implement so I took a crack at it. From some goggling it doesn't seem like there is a straight forward way to "tell" the Textbox to scroll itself to the end. So I thought of it a different way. All framework controls in WPF have a default Style/ControlTemplate, and judging by the looks of the Textbox control there must be a ScrollViewer inside which handles the scrolling. So, why not just work with a local copy of the default Textbox ControlTemplate and programmaticlly get the ScrollViewer. I can then tell the ScrollViewer to scroll its Contents to the end. Turns out this idea works.

Here is the test program I wrote, could use some refactoring but you can get the idea by looking at it:

Here is the XAML:

  
    
    
    
    
    
    
      
        
      
      
        
          
          
          
        
      
    
    

  
  
    test
  

And the code behind:

using System;
using System.Windows;
using System.Windows.Controls;

namespace WpfApplication3
{
    /// 

    /// Interaction logic for MainWindow.xaml
    /// 
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            for (int i = 0; i < 10; i++)
            {
                textbox.AppendText("Line " + i + Environment.NewLine);
            }
        }
    }

    public class AutoScrollTextBox : TextBox
    {
        protected override void OnTextChanged(TextChangedEventArgs e)
        {
            base.OnTextChanged(e);
            // Make sure the Template is in the Visual Tree: 
            // http://stackoverflow.com/questions/2285491/wpf-findname-returns-null-when-it-should-not
            ApplyTemplate();
            var template = (ControlTemplate) FindResource("MyTextBoxTemplate");
            var scrollViewer = template.FindName("PART_ContentHost", this) as ScrollViewer;
            //SelectionStart = Text.Length;
            scrollViewer.ScrollToEnd();
        }
    }
}