gridview模板列里listbox绑定问题：未将对象引用设置到对象的实例

Question

gridview里的部分代码：  
<asp:TemplateField HeaderText="绑定的会议室">
                                <ItemStyle Width="100px" />
                                <ControlStyle Width="100px" />
                                <EditItemTemplate>
                                <asp:ListBox ID="ListBox1" runat="server" SelectionMode="Multiple"></asp:ListBox>
                                </EditItemTemplate>
                                <ItemTemplate>
                                <asp:Label ID="lb_state" runat="server" Text='<%# Bind("room_name") %>'></asp:Label>
                                </ItemTemplate>
                                </asp:TemplateField>
                                <asp:CommandField HeaderText="更新"  ShowEditButton="True" CausesValidation="False"  ItemStyle-Width="120px"> 
                                </asp:CommandField>  CODE代码：
  
    protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            string sql3 = "select room_id,room_name from room_list";
            ListBox ListBox2 = (ListBox)e.Row.FindControl("ListBox1");
            ListBox2.DataSource = dataOperate.getDataset(sql3);
            ListBox2.DataTextField = "room_name";
            ListBox2.DataValueField = "room_id";
            ListBox2.DataBind();
            LinkButton lkbDel = (LinkButton)e.Row.FindControl("lbtnDelete");
            lkbDel.Attributes.Add("OnClick", "javascript:return confirm('确定要删除该管理员吗？')");
            Label lb1 = (Label)e.Row.Cells[0].FindControl("lable");
            lb1.Text = (GridView1.PageIndex * GridView1.PageSize + e.Row.RowIndex + 1).ToString();
        }
    }错误提示：未将对象引用设置到对象的实例
源错误: 
行 74:             string sql3 = "select room_id,room_name from room_list";
行 75:             ListBox ListBox2 = (ListBox)e.Row.FindControl("ListBox1");
行 76:             ListBox2.DataSource = dataOperate.getDataset(sql3);行 77:             ListBox2.DataTextField = "room_name";
行 78:             ListBox2.DataValueField = "room_id";76行出错

Answer 1

ListBox1 只有在编辑状态下才有

Answer 2

把根ListBox1相关的操作放到状态判断后的语句块中：
if (e.Row.RowState == DataControlRowState.Edit)
{
  ListBox ListBox2 = (ListBox)e.Row.FindControl("ListBox1");
  ..
}