【求解】为何直接提交表单不显示验证消息，而ASP Button单击事件处理方法中的验证却可以显示验证消息
问题描述：
页面中共有4个控件(textBox1,CustomValidator1,input button单击提交,asp button 单击验证)
后台有3个方法（Pageload，CustomValidator1_ServerValidate，Button1_Click）
CustomValidator1_ServerValidate和Button1_Click的处理内容相近；
操作流程：
首先，在textbox1中输入错误的内容，然后分别执行：
单击input button提交表单后，页面内容中不显示 验证错误消息；
单击asp button后，页面内容显示验证错误消息；
Form：

XML code

    <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>

Cs：

C# code

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/>");        }    }

[解决办法]
[code=C#][/code] <asp:Button ID="bt_operateItem" runat="server" Text="aa" ValidationGroup="item"
CssClass="confirm" OnClick="bt_operateItem_Click" Style="height: 22px; line-height: 20px;" />
<asp:ValidationSummary ID="ValidationSummary1" ValidationGroup="item" ShowMessageBox="true"
ShowSummary="false" runat="server" />