How do I find what text had been added with TextChanged

Question

I\'m looking to synchronize between a text in the textbox and string in a variable. I found how to get the index in which the string was changed (in the textbox), the length add

Answer 1

If you want only text added you can do this

 string AddedText;
 private void textbox_TextChanged(object sender, TextChangedEventArgs e)
 {
     var changes = e.Changes.Last();
     if (changes.AddedLength > 0)
     {
         AddedText = textbox.Text.Substring(changes.Offset,changes.AddedLength);
     }
 }

Edit

If you want all added and remove text you can do this

    string oldText;
    private void textbox_GotFocus(object sender, RoutedEventArgs e)
    {
        oldText = textbox.Text;
    }

    string AddedText;
    string RemovedText;
    private void textbox_TextChanged(object sender, TextChangedEventArgs e)
    {
        var changes = e.Changes.Last();
        if (changes.AddedLength > 0)
        {
            AddedText = textbox.Text.Substring(changes.Offset, changes.AddedLength);
            if (changes.RemovedLength == 0)
            {
                oldText = textbox.Text;
                RemovedText = "";
            }
        }
        if (changes.RemovedLength > 0)
        {
            RemovedText = oldText.Substring(changes.Offset, changes.RemovedLength);
            oldText = textbox.Text;
            if (changes.AddedLength == 0)
            {
                AddedText = "";
            }
        }
    }