ASP.NET

<asp:GridView ID="DataGridProduct" runat="server" <code>OnSelectedIndexChanged="DataGridProduct_SelectedIndexChanged"</code> AutoGenerateColumns="False">
<Columns>
   <asp:CommandField ButtonType="Image" ShowSelectButton="True" HeaderText="View" />
   <asp:BoundField DataField="ProdCode" HeaderText="Code" ReadOnly="True" SortExpression="ProdCode"
   </asp:BoundField>
   <asp:BoundField DataField="ProdDesc" Visible="False" />
        <asp:TemplateField>
              <HeaderTemplate>Description&lt;/HeaderTemplate>
              <ItemTemplate><%# Limit(Eval("ProdDesc"),25)%></ItemTemplate>
        </asp:TemplateField>
</Columns>

<cc1:ModalPopupExtender <code>ID="mpeProduct"</code> runat="server" TargetControlID="Button1" PopupControlID="panelProduct" CancelControlID="btnClose" BackgroundCssClass="modalBackground" PopupDragHandleControlID="panelDrag" Drag="true">
                    </cc1:ModalPopupExtender>

protected void DataGridProduct_SelectedIndexChanged(object sender, EventArgs e)
{
      if (DataGridProduct.SelectedDataKey[4].ToString() == "Horizontal")
      {
           lblProductCode.Text = DataGridProduct.SelectedDataKey[0].ToString();
           lblProductName.Text = DataGridProduct.SelectedDataKey[1].ToString();
           txtProductSpec.Text = DataGridProduct.SelectedDataKey[2].ToString();
           txtProductDescription.Text = DataGridProduct.SelectedDataKey[3].ToString();
           ImgDisplay.ImageUrl = DataGridProduct.SelectedDataKey[5].ToString().Trim();
           <code>mpeProduct.Show();</code>
       }
}

<%@ Register TagPrefix="users" TagName="YearDropdownList" Src="~/UserControls/YearListBox1.ascx" %>

<td width="80" align="left"><users:YearDropdownList ID="ddlYear" runat="server" ToolTip="Select a Year" OnSelectedIndexChanged="ddlYear_SelcetedIndexChanged" /></td>

<asp:DropDownList ID="ddlYear" runat="server" Enabled="true" Width="75px" AutoPostBack="true" CssClass="dropdown" ToolTip="Select a Year." OnSelectedIndexChanged="ddlYear_SelectedIndexChanged" />

protected void dd1Year_SelectedIndexChanged(Object sender, EventArgs e)
{
//callling string from my user control
sYear = ddlYear.SelectedValue.Trim();
}