private void OnListIndexChanged(object sender, EventArgs e)
     {
         this.EditButton.Enabled = false;
         this.DeleteButton.Enabled = false;
 
         var indices = this.List.SelectedIndices;
         if (indices.Count != 1)
         {
             return;
         }
 
         var index = indices[0];
         var item = this.List.Items[index];
 
         if PropertyName  != null)
         {
             this.EditButton.Enabled = PropertyName.CanEdit(item.Text);
             this.DeleteButton.Enabled = this.CanDelete(item.Text);
         }
 
     }