无法从代码后面访问按钮 [英] Cant access button from behind code

问题描述

这背后的代码

 受保护的  Sub  gvData_RowCommand（ ByVal  sender 作为 对象 ， ByVal  e  As  System.Web.UI.WebControls.GridViewCommandEventArgs）句柄 gvData.RowCommand 
 '  lblError.Text = 
 
  Dim  oButton  As  Button = fvData.FindControl（  BtnRevisi）
 
 ' < span class =code-comment> Dim oTextbox As TextBox = DirectCast（Me.fvData.FindControl（txtRevisi），TextBox） 
 lblError.Visible = 发lse  
 如果 e.CommandName =  选择 然后 
 fvData.ChangeMode（FormViewMode.Edit）
 fvData.Caption =  编辑数据 
 oButton.Visible = 错误 
 结束 如果 
 如果 e.CommandName =   Revisi 然后 
 
 结束 如果 
 
 结束  Sub  
 

这是在HTML上

 <   pre  >  <   asp：FormView     ID   =  fvData    runat   =  server    DataSourceID   =  sdsForm  
   
           DefaultMode   = 编辑   宽度  =  100％    DataKeyNames   =   ID >  
 <   EditItemTemplate  >  
 <  表    cellpadding   =   0   cellspacing   =   0   width   =  100％ >  
 <   tr  >  
 <   td     colspan   =  2 < span class =code-keyword>>  
 <   hr     /  >  
 < span class =code-keyword><   / td  >  
 <   / tr  >  
 
 <   tr  >  
 <   td     colspan   =  2 >  
 <   / td  >  
 <   / tr  >  
 <   tr  >  
 < span class =code-keyword><   td     colspan   = < span class =code-keyword> 2    class   =  FooterStyle >  
 <   uc1：BtnUpdate     ID   =  BtnUpdate1    runat   =  server    /  >  
 <   uc2：BtnDelete     ID   = < span class =code-keyword> BtnDelete1    runat   =  server    /  >  
 <   uc3：BtnCancel     ID   =  BtnCancel1    runat   =  server    /  >  
 
 <  < span class =code-leadattribute> asp：Button     ID   =  btnRevisi < span class =code-attribute>   runat   =  server    OnClick   =   btnSave_Click   样式  =  font-size：8pt;游标：指针;背景位置：左; background-image：url（../ images / Save.gif）; background-repeat：no-repeat; text-align：right;   文字  =  Revisi   工具提示  = 保存    ValidationGroup   = 定价   宽度  =  55px     /  >  
 
 <   / td   >  
 <   / tr  >  
 <   tr  >  
 <   td     colspan   =  2 >  
 < ;   hr     /  < span class =code-keyword>>  
 <   / td  >  
 <   / tr  >  
 <   / table  >  
 <   / EditItemTemplate  >  

本质上我只是想从btnRevisi中获取id属性，因为btnRevisi的位置在formview中，所以btnRevisi的id可以不被称呼。运行后显示错误是btnRevisi没有任何对象引用没有设置为对象的实例。



我尝试了什么：



我已经使用DirectCast声明，结果是相同的（对象引用没有设置为对象的实例）。像这样代码Dim oButton As Button = fvData.FindControl（btnRevisi）



oButton.Visible = False在本节中它的错误

解决方案

您要查找的按钮位于 EditItemTemplate 。



在 FormView 更改为编辑模式并绑定到其数据源之前，不会创建该模板中的控件。



这样的东西应该有效：

 如果 e.CommandName =  选择 然后 
 fvData.Caption =  编辑数据 
 fvData.ChangeMode（FormViewMode.Edit）
 fvData.DataBind（）
 
  Dim  oButton  As  Button = fvData .FindControl（<温泉n class =code-string>  btnRevisi）
 oButton.Visible =  False  
 结束 如果 

但是，如果您所做的只是设置按钮的可见性，您可以在标记中执行此操作：

 <   asp：按钮    ID   =  btnRevisi    runat   =  server   可见  =  False    ...  

this behind code

Protected Sub gvData_RowCommand(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewCommandEventArgs) Handles gvData.RowCommand
       'lblError.Text = ""

       Dim oButton As Button = fvData.FindControl("BtnRevisi")

       'Dim oTextbox As TextBox = DirectCast(Me.fvData.FindControl("txtRevisi"), TextBox)
       lblError.Visible = False
       If e.CommandName = "Select" Then
           fvData.ChangeMode(FormViewMode.Edit)
           fvData.Caption = "Edit Data"
           oButton.Visible = False
       End If
       If e.CommandName = "Revisi" Then

       End If

   End Sub

this is on html

<pre><asp:FormView ID="fvData" runat="server" DataSourceID="sdsForm"

    DefaultMode="Edit" Width="100%" DataKeyNames="ID">
    <EditItemTemplate>
        <table cellpadding=0 cellspacing=0 width="100%">
            <tr>
                <td colspan="2">
                    <hr />
                </td>
            </tr>

            <tr>
                <td colspan="2">
                     </td>
            </tr>
            <tr>
                <td colspan="2" class="FooterStyle">
                    <uc1:BtnUpdate ID="BtnUpdate1" runat="server" />
                    <uc2:BtnDelete ID="BtnDelete1" runat="server" />
                    <uc3:BtnCancel ID="BtnCancel1" runat="server" />

                    <asp:Button ID="btnRevisi" runat="server" OnClick="btnSave_Click" Style="font-size: 8pt; cursor: pointer; background-position: left; background-image: url(../images/Save.gif); background-repeat: no-repeat; text-align: right;" Text="Revisi" ToolTip="Save" ValidationGroup="Pricing" Width="55px" />

                </td>
            </tr>
            <tr>
                <td colspan="2">
                    <hr />
                </td>
            </tr>
        </table>
    </EditItemTemplate> 

in essence I just want to grab the id property from the btnRevisi, because the location of the btnRevisi is in the formview, so the id of the btnRevisi can not be called. and display error after the run is btnRevisi it is nothing Object reference not set to an instance of an object.

What I have tried:

I have declare by using DirectCast, the result is the same still (Object reference not set to an instance of an object). like this the code Dim oButton As Button = fvData.FindControl("btnRevisi")

oButton.Visible = False in this section its an error

解决方案

The button you're trying to find is in the EditItemTemplate.

The controls in that template aren't created until the FormView is changed to "edit" mode and bound to its data source.

Something like this should work:

If e.CommandName = "Select" Then
    fvData.Caption = "Edit Data"
    fvData.ChangeMode(FormViewMode.Edit)
    fvData.DataBind()
    
    Dim oButton As Button = fvData.FindControl("btnRevisi")
    oButton.Visible = False
End If

However, if all you're doing is setting the visibility of the button, you can do that in the markup:

<asp:Button ID="btnRevisi" runat="server" Visible="False" ...

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