请教关于验证控件与插入注册信息时的问题。

我用DW2004做的用户注册过程执行时没总题，后来在用户名、密码、重复密码处加了验证控件，其验证效果显示也是正确的。可不知道为什么，在验证未通过时，我看数据库里却照样可以写入（ACCESS），不知道是什么原因，是否哪里还需要手写代码，这里把代码全贴出，希望大家多指点，谢谢！
<%@ Page Language="C#" ContentType="text/html" ResponseEncoding="gb2312" %>
<%@ Register TagPrefix="MM" Namespace="DreamweaverCtrls" Assembly="DreamweaverCtrls,version=1.0.0.0,publicKeyToken=836f606ede05d46a,culture=neutral" %>
<MM:Insert
runat="server"
CommandText='<%# "INSERT INTO sc8user (sc8pw, sc8user) VALUES (?, ?)" %>'
ConnectionString='<%# System.Configuration.ConfigurationSettings.AppSettings["MM_CONNECTION_STRING_sc8"] %>'
DatabaseType='<%# System.Configuration.ConfigurationSettings.AppSettings["MM_CONNECTION_DATABASETYPE_sc8"] %>'
Expression='<%# Request.Form["MM_insert"] == "form1" %>'
CreateDataSet="false"
Debug="true"
>
<Parameters>
  <Parameter Name="@sc8pw" Value='<%# ((Request.Form["scpw"] != null) && (Request.Form["scpw"].Length > 0)) ? Request.Form["scpw"] : "" %>' Type="WChar" />  
  <Parameter Name="@sc8user" Value='<%# ((Request.Form["scuser"] != null) && (Request.Form["scuser"].Length > 0)) ? Request.Form["scuser"] : "" %>' Type="WChar" />  
</Parameters>
</MM:Insert>
<MM:DataSet 
id="DataSet1"
runat="Server"
IsStoredProcedure="false"
ConnectionString='<%# System.Configuration.ConfigurationSettings.AppSettings["MM_CONNECTION_STRING_sc8"] %>'
DatabaseType='<%# System.Configuration.ConfigurationSettings.AppSettings["MM_CONNECTION_DATABASETYPE_sc8"] %>'
CommandText='<%# "SELECT sc8user FROM sc8user WHERE sc8user = ?" %>'
Debug="true"
>
  <Parameters>
    <Parameter  Name="@sc8user"  Value='<%# ((Request.Form["scuser"] != null) && (Request.Form["scuser"].Length > 0)) ? Request.Form["scuser"] : "" %>'  Type="WChar"   />  
  </Parameters>
</MM:DataSet>
<MM:PageBind runat="server" PostBackBind="true" />
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>收藏吧</title>
<link href="csssc8.css" rel="stylesheet" type="text/css">
</head>
<body>
<br>
<br>
<table width="500" border="0" align="center" cellpadding="0" cellspacing="0">
  <tr>
    <td height="40" align="center">新用户注册</td>
  </tr>
  <tr>
    <td><form name='form1' runat='server' action="" method='POST'><table width="100%"  border="0" align="center" cellpadding="0" cellspacing="0">
      <tr>
        <td width="36%" align="right">用 户 名：</td>
        <td width="64%" height="30"><asp:TextBox ID="scuser" runat="server" TextMode="SingleLine" Columns="18" />　<asp:RequiredFieldValidator ControlToValidate="scuser" Display="Dynamic" ErrorMessage="用户名不能为空！" ID="controlscuser" runat="server" Text="用户名不能为空！" /><asp:CustomValidator ClientValidationFunction="IIf(DataSet1.RecordCount>0,FALSE,TRUE)" ControlToValidate="scuser" Display="Dynamic" ErrorMessage="用户名已存在！" ID="Customcsuser" runat="server"></asp:CustomValidator></td>
      </tr>
      <tr>
        <td align="right">密　　码：</td>
        <td height="30"><asp:TextBox ID="scpw" runat="server" TextMode="Password" Columns="18" />　<asp:RequiredFieldValidator ControlToValidate="scpw" Display="Dynamic" ErrorMessage="密码不能为空！" ID="controlscpw" runat="server" Text="密码不能为空！" /></td>
      </tr>
  <tr>
        <td align="right">重复密码：</td>
        <td height="30"><asp:TextBox ID="scpw2" runat="server" TextMode="Password" Columns="18" />　<asp:RequiredFieldValidator ControlToValidate="scpw2" Display="Dynamic" ErrorMessage="请再一次输入密码！" ID="controlscpw2" runat="server" Text="请再输一次密码！" /><asp:CompareValidator ControlToCompare="scpw" ControlToValidate="scpw2" Display="Dynamic" ErrorMessage="请输入相同的密码！" ID="compscpw" Operator="Equal" runat="server" Text="请输入相同的密码！" Type="String" ValueToCompare="scpw" /></td>
      </tr>
      <tr>
        <td align="right">&nbsp;</td>
        <td height="40"><input type="submit" name="Submit" value="注　册">
          <input type="reset" name="Submit2" value="重　置"></td>
      </tr>
      <tr>
        <td>&nbsp;</td>
        <td>&nbsp;</td>
      </tr>
    </table>
        <input type="hidden" name="MM_insert" value="form1">
    </form></td>
  </tr>
</table></body>
</html>