定製驗證不工作（VB .NET）

Question

下面是自定義的驗證碼

<asp:CustomValidator ID="ModelValidator" runat="server" 
         ErrorMessage="Model is required." 
         ForeColor="Red" ValidateEmptyText="true" 
        OnServerValidate="Model_Validate" ></asp:CustomValidator> 

代碼

Protected Sub Model_Validate(source As Object, args As ServerValidateEventArgs) Handles ModelValidator.ServerValidate 
      Dim value As String = txtModel.SelectedItem.Text 
      If value = "--None--" Then 
       args.IsValid = False 
      End If 

     End Sub 

它運行良好，但沒有顯示錯誤

Answer 1

在你身後應檢查page.IsValid如下：

Protected Sub Model_Validate(source As Object, args As ServerValidateEventArgs) Handles ModelValidator.ServerValidate 
If Page.IsValid Then 
Dim value As String = txtModel.SelectedItem.Text 
      If value = "--None--" Then 
       args.IsValid = False 
      End If 
End If   
End Sub