reordering silverlight datgrid column

Question

i was just reordering the columns of a silverlight datagrid in xaml.cs in the event

grid_autogenerating.i used the follwing code but stil it doesn't works out.

i was using

 void  grid_AutoGeneratingColumn(object sender, DataGridAutoGeneratingColumnEventArgs e)
        {

            switch (e.Column.Header.ToString())
            {
                case "Age":
                    {
                        e.Column.Visibility = Visibility.Visible;
                        e.Column.DisplayIndex = 1;

                        break;
                    }

                case "AgeType":
                    {
                        e.Column.Visibility = Visibility.Visible;
                        e.Column.DisplayIndex = 2;
                        break;
                    }
    }}