jQuery Ajax上传文件

//保存
function btnAdd() {
    var formData = new FormData($("#frm")[0]);

    $.ajax({
        url: "/Admin/ContentManage/SaveEdit",
        type: "POST",
        data: formData,
        contentType: false, //必须false才会避开jQuery对 formdata 的默认处理 XMLHttpRequest会对 formdata 进行正确的处理   
        processData: false, //必须false才会自动加上正确的Content-Type
        success: function (data) {
            if (data == "OK") {
                alert("保存成功");
                $.iDialog("close"); //刷新父页面
            }
            else {
                alert("保存失败：" + data);
            }
        }
    });
}

//首先判断路径是否存在,不存在则创建路径
string path = Path.Combine(System.Configuration.ConfigurationManager.AppSettings["UploadsFiles"], folder + "/" + DateTime.Now.ToString("yyyyMMdd") + "/");
string physicalPath = server.MapPath(path);
if (!Directory.Exists(physicalPath))
{
    Directory.CreateDirectory(physicalPath);
}

HttpPostedFileBase file = request.Files[0];
string newFileName = Guid.NewGuid().ToString().Replace("-", "") + Path.GetExtension(file.FileName);
string savePath = Path.Combine(physicalPath, newFileName);
file.SaveAs(savePath);
fileName = file.FileName;
string url = Path.Combine(path, newFileName);
return url;