<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataKeyNames="ProductID"
    DataSourceID="SqlDataSource1">
    <Columns>
        <asp:BoundField DataField="ProductID" HeaderText="ProductID" InsertVisible="False"
            ReadOnly="True" SortExpression="ProductID" />
        <asp:BoundField DataField="ProductName" HeaderText="ProductName" SortExpression="ProductName" />
        <asp:BoundField DataField="SupplierID" HeaderText="SupplierID" SortExpression="SupplierID" />
        <asp:BoundField DataField="CategoryID" HeaderText="CategoryID" SortExpression="CategoryID" />
        <asp:TemplateField>
            <ItemTemplate>
                <asp:CheckBox ID="chk_Del" runat="server" />
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>

<script type="text/javascript">
    //根据传入的checkbox的选中状态设置所有checkbox的选中状态
    function selectAll(obj)
    {
        var allInput = document.getElementsByTagName("input");
        //alert(allInput.length);
        var loopTime = allInput.length;
        for(i = 0;i < loopTime;i++)
        {
            //alert(allInput[i].type);
            if(allInput[i].type == "checkbox")
            {
                allInput[i].checked = obj.checked;
            }
        }
    }
</script>

//判断是否选中记录，用户确认删除
function judgeSelect()
{
    var result = false;
    var allInput = document.getElementsByTagName("input");
    var loopTime = allInput.length;
    for(i = 0;i < loopTime;i++)
    {
        if(allInput[i].checked)
        {
            result = true;
            break;
        }
    }
    if(!result)
    {
        alert("请先选则要删除的记录！");
        return result;
    }
    result = confirm("你确认要删除选定的记录吗？");
    return result;
}

2通过服务器端代码实现全选