C#

&lt;html xmlns="http://www.w3.org/1999/xhtml" &gt;<br />
&lt;head runat="server"&gt;<br />
    &lt;title&gt;Untitled Page&lt;/title&gt;<br />
    &lt;script type="text/javascript"&gt;<br />
<br />
    function SelectAll(id) {<br />
    var frm = document.forms[0];<br />
    for (i=0;i&lt;frm.elements.length;i++) {<br />
    if (frm.elements[i].type == "checkbox") {<br />
     frm.elements[i].checked = document.getElementById(id).checked;<br />
             }<br />
        }<br />
    }  <br />
&lt;/script&gt;<br />
&lt;/head&gt;<br />
&lt;body&gt;<br />
    &lt;form id="form1" runat="server"&gt;<br />
    &lt;div&gt;<br />
&lt;asp:GridView ID="GridView1" runat="server" Width="400px" AutoGenerateColumns="False" OnRowDataBound="GridView1_RowDataBound"&gt;<br />
    &lt;Columns&gt;<br />
        &lt;asp:BoundField DataField="PersonID" HeaderText="PersonID" InsertVisible="False"<br />
                ReadOnly="True" /&gt;<br />
        &lt;asp:BoundField DataField="Name" HeaderText="Name" SortExpression="Name" /&gt;<br />
        &lt;asp:TemplateField&gt;<br />
            &lt;%--&lt;AlternatingItemTemplate&gt;<br />
                &lt;asp:CheckBox ID="CheckBox1" runat="server" /&gt;<br />
            &lt;/AlternatingItemTemplate&gt;--%&gt;<br />
            &lt;ItemTemplate&gt;<br />
                &lt;asp:CheckBox ID="CheckBox1" runat="server" /&gt;<br />
            &lt;/ItemTemplate&gt;<br />
            &lt;HeaderTemplate&gt;<br />
                &lt;asp:CheckBox ID="cbSelectAll" runat="server" Text="Select All" /&gt;<br />
            &lt;/HeaderTemplate&gt;<br />
            &lt;HeaderStyle HorizontalAlign="Left" /&gt;<br />
            &lt;ItemStyle HorizontalAlign="Left" /&gt;<br />
        &lt;/asp:TemplateField&gt;<br />
    &lt;/Columns&gt;<br />
&lt;/asp:GridView&gt;<br />
    &lt;/div&gt;<br />
    &lt;/form&gt;<br />
&lt;/body&gt;<br />
&lt;/html&gt;