<form id="form1" runat="server">
    <div>
    <asp:TextBox runat="server" ID="textBox1" ontextchanged="textBox1_TextChanged" ></asp:TextBox>
        <asp:CustomValidator ID="CustomValidator1" runat="server"  
            ControlToValidate="textBox1" ValidateEmptyText="true" 
            ErrorMessage="CustomValidator" EnableClientScript="true" 
            onservervalidate="CustomValidator1_ServerValidate"></asp:CustomValidator>
            <input type="button" onclick="form1.submit();" value="TestSubmit" />
        <asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Button" />
            
        <asp:ValidationSummary ID="ValidationSummary1" runat="server" DisplayMode="BulletList" ShowMessageBox="true"  EnableClientScript="true"/>
    
    </div>
    </form>

public partial class TestValidate : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            ValidationSummary1.HeaderText = "test";
            ValidationSummary1.ValidationGroup += CustomValidator1.ID;
        }

        protected void CustomValidator1_ServerValidate(object source, ServerValidateEventArgs args)
        {
            CustomValidator1.IsValid = textBox1.Text == "123";
            Response.Write("验证了<br/>");
        }

        protected void Button1_Click(object sender, EventArgs e)
        {
            Response.Write("Button<br/>");
            CustomValidator1.IsValid = textBox1.Text == "123";
            Response.Write("验证了<br/>");
        }
    }