How to get checkbox checked value

Hello friend,
i bind value to checkbox property. this checkbox i gave inside gridview.
plz tell me how to get this checkbox valye on this checkchanged event.
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataKeyNames="Asto_Id" EnableModelValidation="True" style="width:100%" > <Columns> <asp:TemplateField><ItemTemplate> <asp:CheckBox ID="ChkConsultancy" runat="server" AutoPostBack="true" OnCheckedChanged="ChkConsultancy_CheckedChanged" Checked='<%# Eval("Charges") %>' /> <ajaxcontrol:MutuallyExclusiveCheckBoxExtender ID="MChk" TargetControlID="ChkConsultancy" runat="server" Key="ME"></ajaxcontrol ...