Configuring The ObjectDataSource For Sorting?

System.NotSupportedException was unhandled by user code
Message=The data source does not support sorting.
Source=namespace
StackTrace:
at namespace.Admin.ToolkitScriptManager1_AsyncPostBackError(Object sender, AsyncPostBackErrorEventArgs e) in C:projectMaster.cs:line 27
at System.Web.UI.ScriptManager.OnAsyncPostBackError(AsyncPostBackErrorEventArgs e)
at System.Web.UI.PageRequestManager.OnPageError(Object sender, EventArgs e)
at System.Web.UI.TemplateControl.OnError(EventArgs e)
at System.Web.UI.Page.HandleError(Exception e).......

below is my code using for simple gridview and i am only having problem with the sorting and paging is working as expected and i even define the ONSorting event but it still throws me an error: The data source does not support sorting.

namespace mynamespace
{
public class Product
{
private int _id;
public int Id
{
get { return _id; }
set { _id = value; }
}
private string _code;
public string Code
{
get { return _code; }
set { _code = value; }
}
private string _name;

public string Name
{
get { return _name; }
set { _name = value; }
}
<asp:GridView ID="GridView1" runat="server" DataKeyNames="Id"
AutoGenerateColumns="False" OnSorting="gridview1_Sorting" DataSourceID="ObjectDataSource1" >
<Columns>
<asp:CommandField ShowEditButton="True" />
<asp:BoundField DataField="Id" HeaderText="Id"
SortExpression="Id" ReadOnly="True" />
<asp:BoundField DataField="Code" HeaderText="Code"
SortExpression="Code" />
<asp:BoundField DataField="Name" HeaderText="Name"
SortExpression="Name" />
<asp:TemplateField HeaderText="State/Province" SortExpression="StateProvinceName".......