初学者的问题

<form id="form1" runat="server">
    <div>
        <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False"
            ShowHeader="False" Width="588px"
            onselectedindexchanged="GridView1_SelectedIndexChanged">
        <Columns>
        <asp:BoundField DataField="projectID" HeaderText="projectID" InsertVisible="False" SortExpression="projectID" />
        <asp:BoundField DataField="projectname" HeaderText="projectname" SortExpression="projectname" />
        <asp:TemplateField>
        <ItemTemplate>
            <asp:CheckBox ID="CheckBox1" runat="server" />
        </ItemTemplate>
        </asp:TemplateField>
        </Columns>
        </asp:GridView>
        <table width="588px" border="1">
       <tr>
       <td>
           <asp:Button ID="Button1" runat="server" Text="我要投票" Width="50%" OnClick="Button1_Click" /></td>
       <td>
           <asp:Button ID="Button2" runat="server" Text="查看投票" Width="50%" /></td>
       </tr>
       <tr>
       <td>
           <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
       </td>
       </tr>
      </table>
    </div>
    </form>
怎样在点击button按钮时在后台代码接受checkbox的值 谢谢