<form id="form1" runat="server">
    <asp:Label ID="lblNamerequired" runat="server" Text="*Name :"></asp:Label>
    <asp:TextBox ID="txtNamerequired" runat="server" ValidationGroup="Validation"></asp:TextBox>
    <asp:requiredFieldValidator ID="requiredFieldValidatorName" runat="server" ControlToValidate="txtNamerequired"
        Display="None" ErrorMessage="Name is required" ValidationGroup="Validation"></asp:requiredFieldValidator>
    <br />
    <asp:Label ID="lblGenderrequired" runat="server" Text="*Gender :"></asp:Label>
    <asp:DropDownList ID="ddlGenderrequired" runat="server" ValidationGroup="Validation">
        <asp:ListItem Selected="True" Value="-1">--Select--</asp:ListItem>
        <asp:ListItem Value="0">Male</asp:ListItem>
        <asp:ListItem Value="1">Female</asp:ListItem>
    </asp:DropDownList>
    <asp:CompareValidator ID="CompareValidatorGender" runat="server" ControlToValidate="ddlGenderrequired"
        Display="None" ErrorMessage="Gender is required" Operator="NotEqual" ValidationGroup="Validation"
        ValueToCompare="-1"></asp:CompareValidator>
    <br />
    <asp:Label ID="lblValidation" runat="server" Text="Fields marked with * are required"></asp:Label>
    <br />
    <asp:Button ID="btnValidate" runat="server" Text="Validate Input" ValidationGroup="Validation" />
    <br />
    <asp:ValidationSummary ID="ValidationSummary1" runat="server" ShowMessageBox="True"
        ShowSummary="False" ValidationGroup="Validation" />
    </form>

您应该在所有验证控件上使用相同的ValidationGroup文本,并使用ValidationGroup和ShowMessageBox =“true”添加ValidationSummary