How Can I Add Footer In Gridview

Telerik RadGrid provides a method to define aggregates on a per column basis from design time and render the results inside the respective column's footer. Aggregate calculations are supported for GridBoundColumns and GridCalculatedColumns.

Steps:-

--Subscribe to the your DataBound event of Grid
--Iterate through the rows in the underlying grid source
--Sum up the total and insert it in the respective column footer

aspx-

<telerik:RadGrid ID="RG1" runat="server">
  <MasterTableView AutoGenerateColumns="False" ShowFooter="True" AllowPaging="true">
    <FooterStyle BackColor="#cc6633"></FooterStyle>
    <Columns>
      <telerik:GridBoundColumn HeaderText="Item Count" DataField="Item Count" UniqueName="Item Count" />
    </Columns>
  </MasterTableView>
  <PagerStyle Mode="NextPrevAndNumeric" />
</telerik:RadGrid>

in C#-

private void RadGrid1_ItemDataBound(object sender, Telerik.Web.UI.GridItemEventArgs e)
{
    if (e.Item is GridDataItem)
    {
        GridDataItem dataItem = (GridDataItem)e.Item;
        int fieldValue = int.Parse(dataItem["Item Count"].Text);
        total = total + fieldValue;
    }
    if (e.Item is GridFooterItem)
    {
        GridFooterItem footerItem = (GridFooterItem)e.Item;
        footerItem["Item Count"].Text = "Total: " + total.ToString();
    }
}

protected void RadGrid1_DataBound(object sender, System.EventArgs e)
{
    DataTable gridTable = GetDataTable("SELECT * FROM [Order Details]");

    foreach (DataRow row in gridTable.Rows)
    {
        grandTotal = grandTotal + int.Parse(row["Quantity"]);
    }
    GridFooterItem footerItem = RadGrid1.MasterTableView.GetItems(GridItemType.Footer)[0];
    footerItem["Item Count"].Text = footerItem["Item Count"].Text + "<br> Total for all pages: " + grandTotal.ToString();
}