文本框回车时触发按钮事件(用户控件ascx)

aspx页面中包含多个用户控件（.ascx），控件中又有多个文本框、按钮，当在文本框中输入，敲击键盘回车时，会出现异常！解决办法是当点击文本框时执行要触发的按钮，摘抄部分代码如下：

ascx代码：

< table  width ="80%"  style ="border:1px solid #DFDFDF"  align ="center"  cellpadding ="0"  cellspacing ="0"  bgcolor ="#F5F5F5" >
           < tr >
             < td  height ="26"  colspan ="2"  align ="center"  bgcolor ="#DFDFDF"  class ="homeTitle" ></ td >
             </ tr >
           < tr >  
             < td  width ="35%"  height ="42"  align ="right"  class ="homeTitle" > Password: &nbsp;   </ td >
             < td  width ="65%"  align ="left" > &nbsp; < asp:TextBox  runat ="server"  ID ="tbPwd"  CssClass ="input2"  Width ="139px"  Height ="13px"  TextMode ="Password" ></ asp:TextBox ></ td >
           </ tr >
           < tr >  
             < td  height ="42"  colspan ="2"  align ="center" >
             < asp:Button  runat ="server"  ID ="btnSubmit"  Text ="Submit"  CssClass ="input2"  Width ="58px"  Height ="23px"  OnClick ="btnSubmit_Click"   />
            </ td >
           </ tr >
       </ table >

ascx.cs代码：

  protected   void  Page_Load( object  sender, EventArgs e)
     {
        this.tbPwd.Attributes["onkeypress"] = "if(event.keyCode==13){" + this.btnSubmit.ClientID + ".click();return false;}";
    }

     protected   void  btnSubmit_Click( object  sender, EventArgs e)
     {
         //代码
    }