public string actionA()
{
var resultB = RedirectToRoute(new { controller = "controllerB", action = "Index", userId = user.Id, applicantId = applicant.Id }); //返回string json字符串
var resultC = RedirectToRoute(new { controller = "controllerC", action = "Index", userId = user.Id, applicantId = applicant.Id }); //返回string json字符串
//return resultB和resultC组成一个string返回
}