关于控件中调用js方法时出错

 <asp:TextBox ID="TextBox1" runat="server" OnTextChanged="javascript:TestLen()"></asp:TextBox>错误提示: CS1026: 应输入 )全部代码为：
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="JavaScript.aspx.cs" Inherits="TestJavaScript.JavaScript" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head runat="server">
    <title></title>
</head>
<body>
<script  language="javascript" type="text/javascript">
    function TestLen() {
        alert("Hello");
    }
</script>
    <form id="form1" runat="server">
    <div>
    
    <asp:TextBox ID="TextBox1" runat="server" OnTextChanged="javascript:TestLen()"></asp:TextBox>
    </div>
    </form>
</body>
</html>
JavaScript控件