Working with checkboxes in datagrid in ASP.NET

Question

Hi Frnz
  I have some checkboxes in  Datagrid, out of that datagrid i have a checkbox. if i select that checkbox then i should select all the checkboxes in datagrid. please help me out.
 
<asp:GridView ID="gvApplicable" runat="server" AutoGenerateColumns="False"
AllowSorting="True" AllowPaging="True" PageSize="15" onrowediting="gvApplicable_RowEditing"
onpageindexchanging="gvApplicable_PageIndexChanging" Height="127px"
onselectedindexchanged="gvApplicable_SelectedIndexChanged" Width="213px" >
<Columns>
<asp:TemplateField >
<ItemTemplate>
<asp:CheckBox ID="Chk1" runat="server" />
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField ReadOnly="true" DataField="DeptCode" HeaderText="Code" InsertVisible="false" SortExpression="Code"></asp:BoundField>
<asp:BoundField ReadOnly="true" DataField="DeptName" HeaderText="Category" InsertVisible="false" SortExpression="Name"></asp:BoundField>
</Columns>
</asp:GridView>
<asp:CheckBox ID="CheckBox1" runat="server" AutoPostBack="true" Text="Select" CssClass="TableList"
Height="25px" Width="126px" oncheckedchanged="CheckBox1_CheckedChanged"></asp:CheckBox>