public virtual bool Select(TextPosition start, TextPosition end)
{
if (start == (TextPosition)null && end != (TextPosition)null)
{
throw new ArgumentNullException(nameof(start));
}
if (object.Equals((object)start, (object)end))
{
end = (TextPosition)null;
}
if (object.Equals((object)this.SelectionStart, (object)start) && object.Equals((object)this.SelectionEnd, (object)end))
{
this.SetCaretPosition();
return(false);
}
bool notify = this.SelectionStart != (TextPosition)null;
if (notify)
{
int length = TextPosition.GetLength(start, end);
SelectionChangingEventArgs e = new SelectionChangingEventArgs(this.textBoxElement.SelectionStart, this.SelectionLength, end == (TextPosition)null ? (int)start : Math.Min((int)start, (int)end), length);
this.OnSelectionChanging(e);
if (e.Cancel)
{
return(false);
}
}
this.selectionStart = start;
this.selectionEnd = end;
this.SelectOverride(notify);
return(true);
}
protected virtual void OnSelectionChanging(SelectionChangingEventArgs e)
{
SelectionChangingEventHandler selectionChanging = this.SelectionChanging;
if (selectionChanging == null || this.suspendNotificationCount != 0)
{
return;
}
selectionChanging((object)this, e);
}
private void Navigator_SelectionChanging(object sender, SelectionChangingEventArgs e)
{
this.changed = true;
}