How to check which checkboxes are selected for which row in gridview.

<asp:gridview id="GridView1" runat="server" datasourceid="SqlDataSource1" width="400px" mode="hold" xmlns:asp="#unknown" />
    <Columns>

        <asp:TemplateField>

            <AlternatingItemTemplate>

                <asp:CheckBox ID="CheckBox1" runat="server" />

            </AlternatingItemTemplate>

            <ItemTemplate>

                <asp:CheckBox ID="CheckBox1" runat="server" />

            </ItemTemplate>

            <HeaderTemplate>

                <asp:CheckBox ID="cbSelectAll" runat="server" Text="Select All" />

            </HeaderTemplate>

            <HeaderStyle HorizontalAlign="Left" />

            <ItemStyle HorizontalAlign="Left" />

        </asp:TemplateField>

    </Columns>

</asp:GridView>

protected void GridView1_RowDataBound(object sender, System.Web.UI.WebControls.GridViewRowEventArgs e) {

    if (e.Row.RowType == DataControlRowType.Header) {

      

        //and passing the ClientID of the Select All checkbox

        ((CheckBox)e.Row.FindControl("cbSelectAll")).Attributes.Add("onclick", "javascript:SelectAll('" + ((CheckBox)e.Row.FindControl("cbSelectAll")).ClientID + "')");
// Write your own code here 
    }

}