ASP.NET表单视图（如果正在更新）

我想在更新表单视图之前运行if； 如果是，则…“消息”&取消更新查询 如果没有，请继续更新查询

我已经试过了，但是在if的第一行得到了一个“object instance not set to null instance…”？不管怎样，项目都会更新

Private Sub FormView2_ItemUpdating(sender As Object, e As System.Web.UI.WebControls.FormViewUpdateEventArgs) Handles FormView2.ItemUpdating
    Dim status As TextBox = FormView1.FindControl("ApprovalStatusTextBox")


    If status.Text = "approved" Or "denied" Then
        e.Cancel = True
        lblupdaterequest.Text = "you cannot update this request as it has already been responded to"
    Else
        HolidayDetailsdatasource.Update()
    End If

有谁知道一个更好的方法可以实现这样的目标

确切错误：

   System.NullReferenceException was unhandled by user code
   Message=Object reference not set to an instance of an object.
   Source=WebApplication1
   StackTrace:
   at WebApplication1.HolidayApprovalDetails.DetailsView1_ItemUpdating(Object sender, DetailsViewUpdateEventArgs e) in line 32
   at System.Web.UI.WebControls.DetailsView.OnItemUpdating(DetailsViewUpdateEventArgs e)
   at System.Web.UI.WebControls.DetailsView.HandleUpdate(String commandArg, Boolean causesValidation)
   at System.Web.UI.WebControls.DetailsView.HandleEvent(EventArgs e, Boolean causesValidation, String validationGroup)
   at System.Web.UI.WebControls.DetailsView.OnBubbleEvent(Object source, EventArgs e)
   at System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args)
   at System.Web.UI.WebControls.DetailsViewRow.OnBubbleEvent(Object source, EventArgs e)
   at System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args)
   at System.Web.UI.WebControls.LinkButton.OnCommand(CommandEventArgs e)
   at System.Web.UI.WebControls.LinkButton.RaisePostBackEvent(String eventArgument)
   at System.Web.UI.WebControls.LinkButton.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument)
   at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument)
   at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData)
   at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

---

我至少可以看到您正在从“FormView1”检索状态文本框的值，而您的子项更新是指“FormView2”

更改此选项后，请尝试在if之前添加一个消息框，以确保获得所需的正确值：

MsgBox(status.Text)

---

希望它能帮助您解决问题。

您能发布真实、清晰的错误消息吗？也许是复制粘贴？听起来您的状态文本框不存在或为空？你能调试吗？这个文本框在哪里，我的意思是在哪个模板中（f.e.？

FormView

有三种不同的格式。除此之外，我建议使用此文本框的标题为只读？然后我建议使用。你确定你拼写的

ApprovalStatusTextBox

正确吗？你能显示你的FormView的相关部分吗？它不再崩溃。但不管是什么格式，它仍然会更新“状态”我是不是遗漏了什么？

MsgBox(status.Text)