register.aspx页面代码:

<scripttype="text/javascript">

functioncheckuser()

{

varoption={

parameters:"userid="+$("userid").value,

method:"post",

onSuccess:function(transport){

varrp=transport.responseText;

if(rp=="true")

{

alert("该用户昵称存在！！");

}

else

{

alert("该用户昵称不存在，请重新输入！！");

}

},

onFailure:function(transport){

alert("数据提交失败，请检查网络或重试。");

}

}

varrequest=newAjax.Request("Ajax.aspx?userid="+escape($("userid").value),option);

}

</script>

昵称：<asp:TextBoxID="userid"runat="server"Text=""onblur="checkuser()"></asp:TextBox>

Ajax.aspx页面代码:

privatevoidPage_Load(objectsender,System.EventArgse)

{

stringuserid=Request.QueryString["userid"];

stringsql="selectuseridfromblog_userwhereuserid='"+userid+"')";

objecto=dbconn.ExecuteScalar(sql);

if(o==null)

Response.Write("false");

else

Response.Write("true");

}