JQuery调webservice实现邮箱验证(检测是否可用)

<asp:ScriptManager ID="ScriptManager1" runat="server"> 
<Services> 
<asp:ServiceReference Path="~/WebService1.asmx" /> 
</Services> 
</asp:ScriptManager> 
SinaWeiBo.WebService1.cunzai($(this).val(), a, b) 
{ 
function a(result) { 
if (result == "该邮箱已存在请重新输入") { 
$('#txtusername').val(''); 
$('#txtusername').focus(); 
$('#emailyz').text(result); 
} 
else { $('#emailyz').text('可以使用'); } 
} 
function b() { 
$('#emailyz').text('没有返回值'); 
} 
}

webservice：

public string cunzai(string txtusername) 
{ 
//判断邮箱存不存在 
try 
{ 
SinaWeiBo.BLL.T_Users bt1 = new BLL.T_Users(); 
DataSet ds = new DataSet(); 
ds = bt1.GetList(" T_UserEmail='" + txtusername + "'"); 
string cha = ds.Tables[0].Rows[0][0].ToString(); 
return "该邮箱已存在请重新输入"; 
} 
catch { 
return "正确"; 
} 
}