Display Sort Index for Multi-Column Sorting

This how to article presents a possible solution for displaying sort index of grid columns when multi-column sorting is enabled(AllowMultiColumnSorting="True").

From the code inside grid PreRender event you can see how to represent a numeric sequence of the order in which the columns are sorted.

<telerik:RadGrid RenderMode="Lightweight" runat="server" ID="RadGrid1" OnNeedDataSource="RadGrid1_NeedDataSource" AllowPaging="true"
    OnPreRender="RadGrid1_PreRender" MasterTableView-AllowMultiColumnSorting="true"
     AllowSorting="true">
</telerik:RadGrid>

protected void RadGrid1_NeedDataSource(object sender, GridNeedDataSourceEventArgs e)
{
    DataTable table = new DataTable();
    table.Columns.Add("ID", typeof(int));
    table.Columns.Add("FirstName", typeof(string));
    table.Columns.Add("LastName", typeof(string));
    table.Columns.Add("Age", typeof(int));
    table.Columns.Add("Date", typeof(DateTime));
    table.Columns.Add("BoolValue", typeof(Boolean));
    for (int i = 0; i < 55; i++)
    {
        table.Rows.Add(i, "FirstName" + i, "LastName" + i, 20 + i, DateTime.Now.AddDays(i), i % 2 == 0);
    }

    (sender as RadGrid).DataSource = table;
}

protected void RadGrid1_PreRender(object sender, EventArgs e)
{
    GridHeaderItem headerItem = RadGrid1.MasterTableView.GetItems(GridItemType.Header)[0] as GridHeaderItem;
    int sortIndex = 1;
    foreach (GridSortExpression expression in RadGrid1.MasterTableView.SortExpressions)
    {
        foreach (GridColumn column in RadGrid1.MasterTableView.RenderColumns)
        {
            if (column is IGridDataColumn)
            {
                if (expression.FieldName == (column as IGridDataColumn).GetActiveDataField())
                {
                    TableCell cell = headerItem[column.UniqueName];
                    Literal literal = new Literal();
                    literal.Text = sortIndex.ToString();
                    cell.Controls.Add(literal);
                }
            }
        }

        sortIndex++;
    }
}