GridView编辑功能，更新时无法获得更新值得问题，求指点，谢谢

Question

代码如下
                           <asp:GridView ID="grvTargetList" runat="server" Width="100%" EmptyDataText="没有相关项目信息"
                            AutoGenerateColumns="False" DefaultSort="Target_ID" OnRowEditing="btEdit_Click" OnRowUpdating="btOK_Click"  OnRowCancelingEdit="btCancel_Click">
                           <Columns>
                               
                           
                              
                               <asp:TemplateField HeaderText="指标名称">
                                <EditItemTemplate>
                                    <asp:TextBox ID="tbName" runat="server" Text='<%# Bind("Target_Name") %>'></asp:TextBox>                                
</EditItemTemplate>
                                <ItemTemplate>
                                    <asp:Label ID="lblName" runat="server" Text='<%# Bind("Target_Name") %>'></asp:Label>                                
</ItemTemplate>
                            </asp:TemplateField>
                            
                             <asp:TemplateField HeaderText="指标单位">
                                <EditItemTemplate>
                                    <asp:TextBox ID="tbUnit" runat="server" Text='<%# Bind("Target_Unit") %>'></asp:TextBox>                                
</EditItemTemplate>
                                <ItemTemplate>
                                    <asp:Label ID="lblUnit" runat="server" Text='<%# Bind("Target_Unit") %>'></asp:Label>                                
</ItemTemplate>
                            </asp:TemplateField>
                                
                                 <asp:TemplateField HeaderText="目标值">
                                <EditItemTemplate>
                                    <asp:TextBox ID="tbGoal" runat="server" Text='<%# Bind("Target_Goal") %>'></asp:TextBox>                                
</EditItemTemplate>
                                <ItemTemplate>
                                    <asp:Label ID="lblGoal" runat="server" Text='<%# Bind("Target_Goal") %>'></asp:Label>                                
</ItemTemplate>
                            </asp:TemplateField>
                             
                              <asp:TemplateField HeaderText="权重">
                                <EditItemTemplate>
                                    <asp:TextBox ID="tbWeight" runat="server" Text='<%# Bind("Target_Weight") %>'></asp:TextBox>                                
</EditItemTemplate>
                                <ItemTemplate>
                                    <asp:Label ID="lblWeight" runat="server" Text='<%# Bind("Target_Weight") %>'></asp:Label>                                
</ItemTemplate>
                            </asp:TemplateField>
                              
                            <asp:CommandField HeaderText="编辑" ShowEditButton="True" CausesValidation="False" />                        
                           </Columns>
                               <HeaderStyle Font-Bold="True" Font-Names="宋体" ForeColor="White" Height="20px" HorizontalAlign="Center"
                                VerticalAlign="Middle" />
                                <PagerStyle Font-Bold="True" Font-Names="宋体" ForeColor="White" Height="20px" HorizontalAlign="Center"
                                VerticalAlign="Middle"/>
                       </asp:GridView>
        /// <summary>
        /// 更新按钮按下时
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        protected void btOK_Click(object sender, GridViewUpdateEventArgs e)
        {            GridViewRow loGridRow = this.grvTargetList.Rows[e.RowIndex];
            //这里就会出错了，loGridRow.FindControl("tbName"）为null
            string lsTargetName = ((TextBox)loGridRow.FindControl("tbName")).Text.Trim();
            string lsTargetUnit = ((TextBox)loGridRow.FindControl("tbUnit")).Text.Trim();
            string lsGoal = ((TextBox)loGridRow.FindControl("tbGoal")).Text.Trim();
            string lsWeight = ((TextBox)loGridRow.FindControl("tbWeight")).Text.Trim();
           
            
            //恢复到浏览状态
           
            grvTargetList.EditIndex = -1;
            this.grvTargetList.DataBind(moItemsDs.ProjectTarget);
        }

Answer 1

 string   lsTargetName   =   ((TextBox)loGridRow.Rows[e.RowIndex].cell[0].FindControl("tbName")).Text.Trim(); 

Answer 2

loGridRow.Cells[0].FindControl("tbName") 是null

Answer 3

程序好像没错,加这个试试if (e.Row.RowType == DataControlRowType.DataRow)
{
........
}