To select a item on rightclick using devexpress ListboxControl you need to use the MouseDown Event.
See the samples below.
Sample C#
private void listBoxControl1_MouseDown(object sender, MouseEventArgs e)
{
listBoxControl1.SelectedIndex = listBoxControl1.IndexFromPoint(new Point(e.X, e.Y));
}
Sample VB.NET
Private Sub listBoxControl1_MouseDown(sender As Object, e As MouseEventArgs) listBoxControl1.SelectedIndex = listBoxControl1.IndexFromPoint(New Point(e.X, e.Y)) End Sub