New Post: DateTimePicker popup on TextBox click

 public class MyDateTimePicker : DateTimePicker
  {
    public override void OnApplyTemplate()
    {
      if( this.TextBox != null )
      {
        this.TextBox.PreviewMouseLeftButtonUp -= this.TextBox_PreviewMouseLeftButtonUp;
      }

      base.OnApplyTemplate();

      if( this.TextBox != null )
      {
        this.TextBox.PreviewMouseLeftButtonUp += this.TextBox_PreviewMouseLeftButtonUp;
      }
    }

    private void TextBox_PreviewMouseLeftButtonUp( object sender, MouseButtonEventArgs e )
    {
      this.IsOpen = true;
    }
  }