在jquery.validate 远程验证用户名是否可用

    $("#form1").validate({
        errorElement: "span",
        errorPlacement: function(error, element) {
            var td = element.parent("td").next("td");
            td.html('');
            error.appendTo(td);
        },
        rules: {
            txUsername: {
                required: true,
                remote: {
                    type: "post",
                    url: "Services/Ajax.asmx/CheckUserAvailable",
                    data: {
                        username: $("#txUsername").val()
                    },
                    dataType: "xml",
                    dataFilter: function(dataXML) {
                        var result = $(dataXML).find("boolean").text();
                        if (result == "false")
                            return false;
                        else
                            return true;
                    }
                }
        },
        success: function(label) {
            label.text('').addClass("success");
        },
        messages: {
            txUsername: {
                required: "请输入用户名",
                remote: "用户名已被占用"
            }
        }
    });

[WebMethod]
public bool CheckUserAvailable(string username)
{
     return !AccountService.IsExist(username);
}

最重要的是dataType和dataFilter要写对,否则验证就会没反应