c# - asp.net 中列表框的验证器

Question

<asp:ListBox ID="lst_newGrpMembers" 
             DataValueField="Name" 
             SelectionMode="Multiple"
             Width="120px" 
             ToolTip="Press ctrl to select multiple users" 
             runat="server">
</asp:ListBox>

<asp:RequiredFieldValidator ID="RequiredFieldValidator1" 
                            runat="server" 
                            ControlToValidate="lst_newGrpMembers"
                            ErrorMessage="Atleast one member required" 
                            CssClass="Error" 
                            Text="*Atleast one member required"
                            ValidationGroup="CreateGroupValidationGroup">
</asp:RequiredFieldValidator>

我有一个列表框的必填字段验证器，它验证并显示列表框中没有条目的错误，但是当我将项目添加到列表框时，它仍然显示错误。当我选择我添加的列表框项目并单击提交时，它工作正常。如何验证列表框。

Answer 1

在 RequiredFieldValidator 上，尝试将 InitialValue 设置为空字符串:

<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server"          
    InitialValue=""
    ControlToValidate="lst_newGrpMembers" 
    ErrorMessage="Atleast one member required"  
    CssClass="Error"  
    Text="*Atleast one member required" 
    ValidationGroup="CreateGroupValidationGroup"> 
</asp:RequiredFieldValidator>