各位大大您好，我在gridview的最後一行另外添加了textbox，在點選儲存button時，我用gridview.rows(i).findcontrol("textbox")抓不到textbox，請問如何抓到textbox?

設計如下：

<asp:GridView ID="xxxGridView"... DataKeyNames="...">
<PagerSettings ... Mode="NumericFirstLast" />
<PagerStyle ... HorizontalAlign="Center" />
<Columns runat="server">
<asp:TemplateField HeaderText="xxx"  ItemStyle-HorizontalAlign="Left" >
<HeaderStyle Width="90px" />
<ItemTemplate>
<asp:Label ID="TLabxxx" runat="server" Text='<%#Bind("...") %>'></asp:Label>
 </ItemTemplate>
</asp:TemplateField>                   
<asp:TemplateField HeaderText="xxx">
<HeaderStyle Width="200px" />
<ItemTemplate>                      
<asp:RadioButtonList ID="rdbtnLt1" runat="server" RepeatDirection="Horizontal">
<asp:ListItem>xx</asp:ListItem>
<asp:ListItem>xxx</asp:ListItem>
<asp:ListItem>xxxx</asp:ListItem>
</asp:RadioButtonList>
<asp:HiddenField ID="Hidxxx" runat="server" Value='<%# Bind("...") %>' />
</ItemTemplate>
</asp:TemplateField>
...
<asp:CommandField ... />
</Columns>                                          
<HeaderStyle CssClass="..." />
...
<FooterStyle CssClass="..." />
</asp:GridView>
<asp:Button ID="butsave" runat="server" Text="儲存" />

程式碼如下
設定xxxGridView

Protected Sub setxxxGridView()
...

 Dim gvr As GridViewRow = New GridViewRow(0, -1, DataControlRowType.DataRow, DataControlRowState.Normal)
Dim cell1 As TableCell = New TableCell()
Dim cell2 As TableCell = New TableCell()
Dim tb1 As TextBox = New TextBox()
tb1.ID = "textboxnotep"
tb1.Text = Hidpchknote.Value
tb1.TextMode = TextBoxMode.MultiLine
tb1.Width = 300
tb1.Height = 50
Dim cell3 As TableCell = New TableCell()
Dim tb2 As TextBox = New TextBox()
tb2.ID = "textboxnotec"
tb2.Text = Hidcchknote.Value
tb2.TextMode = TextBoxMode.MultiLine
tb2.Width = 300
tb2.Height = 50
cell1.Text = "備註"
cell2.Controls.Add(tb1)
cell3.Controls.Add(tb2)
gvr.Controls.Add(cell1)
gvr.Controls.Add(cell2)
gvr.Controls.Add(cell3)
gvr.CssClass = "GridView_B_RowStyle"
gvr.Style("text-align") = "left"
xxxGridView.Controls(0).Controls.AddAt(xxxGridView.Rows.Count + 2, gvr)
            
...

End Sub

設定xxxGridView的欄位存進資料庫，其中textbox抓不到

    Protected Sub butsave_click(sender As Object, e As EventArgs) Handles butsave.Click

        savexxxGridView(startid)
    End Sub

Protected Sub savexxxGridView(ByRef startid As String)
...
If Session("CompID") = "1" Then
For m As Integer = 0 To xxxGridView.Rows.Count - 1
Using cn As New SqlConnection(ConnectString)
Dim dt As New DataTable
Dim textboxnotep As TextBox = xxxGridView.Rows(m).FindControl("textboxnotep")

'''系統執行發生錯誤：並未將物件參考設定為物件的執行個體

'''意思就是抓不到textbox

Dim Hidchktype As HiddenField = xxxGridView.Rows(m).FindControl("Hidchktype")
Dim HidTypeID As HiddenField = xxxGridView.Rows(m).FindControl("HidTypeID")
If textboxnotep.Text <> "" Then
sql2 = "Select chktype from DailyCheckNote  where 1=1"
SqlDA2 = New SqlDataAdapter(sql2, cn)
If startid <> "" Then
sql2 += " and startid= @startid"                                SqlDA2.SelectCommand.Parameters.Add("@startid", SqlDbType.NVarChar) SqlDA2.SelectCommand.Parameters("@startid").Value = startid
End If
SqlDA2.SelectCommand.CommandText = sql2
SqlDS2 = New DataSet 'DataSet資料集物件實體化
SqlDA2.Fill(SqlDS2) '填充DataSet資料集
SqlDA2.Fill(dt)
SqlDA2.Dispose()
If Hidchktype.Value <> "" Then
Hidtype = Hidchktype.Value
For h As Integer = 0 To dt.Rows.Count - 1
teststype = dt.Rows(h)(0).ToString()
If HidTypeID.Value = teststype Then
pusernoteupdate(startid, textboxnotep)
End If
Next h
ElseIf Hidchktype.Value = "" Then
pusernoteinsert(startid, cktype, HidTypeID, textboxnotep)
Hidchktype.Value = HidTypeID.Value
End If
Else
End If
End Using
Next
For n As Integer = 0 To xxxGridView.Rows.Count - 1
Using cn As New SqlConnection(ConnectString)
Dim dt As New DataTable
Dim textboxnotec As TextBox = xxxGridView.Rows(n).FindControl("textboxnotec")

'''系統執行發生錯誤：並未將物件參考設定為物件的執行個體

'''意思就是抓不到textbox


Dim Hidchktype As HiddenField = xxxGridView.Rows(n).FindControl("Hidchktype")
Dim HidTypeID As HiddenField = xxxGridView.Rows(n).FindControl("HidTypeID")
If textboxnotec.Text <> "" Then
sql2 = "Select chktype from DailyCheckNote  where 1=1"
SqlDA2 = New SqlDataAdapter(sql2, cn)
If startid <> "" Then
sql2 += " and startid= @startid"
SqlDA2.SelectCommand.Parameters.Add("@startid", SqlDbType.NVarChar)
SqlDA2.SelectCommand.Parameters("@startid").Value = startid
End If
SqlDA2.SelectCommand.CommandText = sql2
SqlDS2 = New DataSet 'DataSet資料集物件實體化
SqlDA2.Fill(SqlDS2) '填充DataSet資料集
SqlDA2.Fill(dt)
SqlDA2.Dispose()
If Hidchktype.Value <> "" Then
Hidtype = Hidchktype.Value
For h As Integer = 0 To dt.Rows.Count - 1
teststype = dt.Rows(h)(0).ToString()
If HidTypeID.Value = teststype Then
cusernoteupdate(startid, textboxnotec)
End If
Next h
ElseIf Hidchktype.Value = "" Then
cusernoteinsert(startid, cktype, HidTypeID, textboxnotec)
Hidchktype.Value = HidTypeID.Value
End If
Else
End If
End Using
Next
End If
end sub

請問各位大大如何抓到textbox，謝謝各位大大！！