c# - error The GridView 'GridView1' fired event Sorting which wasn't handled -

I'm trying to create two groups in the data grid like this example, but there is an error and I do not know Whether it is the reason or how to solve it

The sorting event does not seem to be handled properly. You can handle it in the following way:

  & lt; Asp: GridView id = "GridView1" runat = "server" Allow = "true" honors = "GridView1_Sorting" & gt; & Lt; / ASP: GridView & gt; Protected Zero GridView1_Sorting (Object Sender, GridViewSortEventArgs e) {dataTable.DefaultView.Sort = e.SortExpression; GridView1.DataSource = DataTable; GridView1.DataBind (); }