How i can make header of the gridview intact

See more:

ASP.NET

i have used gridview to show record as

<asp:GridView ID="dgvMaildetail" runat="server" Width="100%" AutoGenerateColumns="False"
                                                       AllowSorting="True" DataKeyNames="md_id" AllowPaging="True" OnPageIndexChanging="dgvMaildetail_PageIndexChanging"
                                                       RowStyle-Height="15px">
                                                       <Columns>
     <asp:TemplateField HeaderText="Subject" SortExpression="md_subject">
                                                               <ItemTemplate>
                                                                   <asp:LinkButton ID="lnksubject" CausesValidation="false"
                                                                        Text='<%#Eval("md_subject") %>'
                                                                       runat="server" Width="50%"></asp:LinkButton>
                                                               </ItemTemplate>
                                                           </asp:TemplateField>
 </Columns>
                                                   </asp:GridView>

but when the source is nothing then entire grid becomes empty

with header also not being shown

please help