You can do this using Javascript function
function CheckOne(obj) {
var grid = obj.parentNode.parentNode.parentNode;
var inputs = grid.getElementsByTagName("input");
for (var i = 0; i < inputs.length; i++) {
if (inputs[i].type == "checkbox") {
if (obj.checked && inputs[i] != obj && inputs[i].checked) {
inputs[i].checked = false;
}
}
}
}
Now Call through Checkbox inside the grid
<ItemTemplate>
<asp:CheckBox ID="ChkSelect" runat="server" onclick="CheckOne(this)" />
</ItemTemplate>