TextBox TextChanged event on programmatic versus user change of text contents

Question

I would like to differentiate between changing the text programmatically (for example in a button click handler event) and user input (typing, cutting and pasting text). <

Answer 1

Partial credits for dodgy_coder (agreed not conform the beautiful design you hope for, but imo the best compromis). Consider everything you want to cover:

1. move text by dragging with mouse from TB2 to TB1
2. cut (ctrl-x, programmatic cut, mouse-menu-cut)
3. paste (ctrl-v, programmatic paste, mouse-menu-paste)
4. undo (ctrl-z, programmatic undo)
5. redo (ctrl-Y, programmatic redo)
6. delete & backspace
7. keyboard text (alfanumeric + symbols + space)

Consider what you want to exclude:

8. programmatic setting of Text
   

Code

public class MyTB : TextBox
{
    private bool _isTextProgrammaticallySet = false;

    public new string Text
    {
        set
        {
            _isTextProgrammaticallySet = true;
            base.Text = value;
            _isTextProgrammaticallySet = false;
        }
    }

    protected override void OnTextChanged(TextChangedEventArgs e)
    {
        base.OnTextChanged(e);

        // .. on programmatic or on user


        // .. on programmatic
        if (_isTextProgrammaticallySet)
        {


            return;
        }

        // .. on user
        OnTextChangedByUser(e);
    }

    protected void OnTextChangedByUser(TextChangedEventArgs e)
    {
        // Do whatever you want.
    }
}

The following is discouraged, but the results of an attempt to cover all:
The alternatives for catching all the events were:

• DataObject.AddPastingHandler(MyTextBox, MyPasteCommand);
  Covers 1 & 3
• OnPreviewTextInput
  Covers 7 but not space
• OnKeyDown
  Covers 7-space

Trying to cover 2, 4, 5, 6 & 8 I figured I should go with the easier and consistent solution above :)