Selection disabled on left click

Hy Team !
I am showing the DropDown menu on focus with this code :

private void RadAutoCompleteBox_GotFocus(object sender, RoutedEventArgs e)
        {
            var autoComplete = (RadAutoCompleteBox)sender;
            string searchText = autoComplete.SearchText;
            if (autoComplete.SelectedItem != null)
            {
                searchText = BindingExpressionHelper.GetValue(autoComplete.SelectedItem, autoComplete.DisplayMemberPath).ToString();
            }
            autoComplete.Populate(searchText);
        }

This works but it also disable the left click when I try to select something from this list. Every other way are working (right click, keyboard control, ...) just the left click doesn't.

So what can I do to fix this issue ?