GridView Sorting is not working

Merged with GridView sorting works once only.

Please help me, I set Allowsorting="true" but sorting is not working in my GridView. I want automatic sorting i.e. sorting without handling its event.

Here is code of aspx page:

<asp:GridView ID="gdvSignatureLines" runat="server" CssClass="Grid1" AutoGenerateColumns="False"
                        SkinID="PagedGridView" AllowPaging="True" AllowSorting="True" DataKeyNames="Id" 
                        onrowcommand="gdvSignatureLines_RowCommand" 
                        onrowdeleting="gdvSignatureLines_RowDeleting" 
                        onrowediting="gdvSignatureLines_RowEditing">
                        <PagerStyle CssClass="gridPager" HorizontalAlign="Right" />
                        <Columns>
                            <ucc:commandfieldcontrol headertext="Actions" showdeletebutton="true" buttontype="Image"
                                deleteimageurl="~/App_Themes/Default/images/delete.png" showeditbutton="true"
                                editimageurl="~/App_Themes/Default/images/edit.png" deleteconfirmationtext="Are you sure you want to delete?">
                                    <ItemStyle HorizontalAlign="Center" Width="60px" />
                             </ucc:commandfieldcontrol>
                            <asp:BoundField DataField="SortOrder" HeaderText="Line" SortExpression="SortOrder" />
                            <asp:TemplateField HeaderText="Type">
                                <ItemTemplate>
                                    <asp:Label ID="lblglTypeId" runat="server" Text='<%# Eval("GeneralLookup.LookupItem") %>'></asp:Label>
                                </ItemTemplate>  
           开发者_开发百科                 </asp:TemplateField>
                            <asp:TemplateField HeaderText="Label">
                                <ItemTemplate>
                                    <asp:Label ID="lblglLabelId" runat="server" Text='<%# Eval("GeneralLookup1.LookupItem") %>'></asp:Label>
                                </ItemTemplate>  
                            </asp:TemplateField>
                            <asp:BoundField DataField="Caption" HeaderText="Caption" SortExpression="Caption" />
                        </Columns>
                        <EmptyDataTemplate>
                            <div class="divEmptyListingGrid">
                                --- No Signature Line Exists ---
                            </div>
                        </EmptyDataTemplate>
                    </asp:GridView>

Here is the code of CS file:

protected void LoadSignatureList(int reportId, string reportName)
{
    lblHeading.Text = "Signature Line for " + reportName;
    ReportOptionsBO reportOptionsBO = new ReportOptionsBO();
    this.gdvSignatureLines.DataSource = reportOptionsBO.GetReportSignatureLineByReportId(reportId);
    this.gdvSignatureLines.DataBind();
}

When I click on the Header of column "Line" or "Caption", nothing happens.

I have one more grid that is working fine. The difference between both is, data is bound to this grid on runtime. But the other grid's datasource is preset.

My current grid has not these options of Enable Paging and Enable Sorting.

Please help as soon as possible.