我有两个问题：

What is the difference between JSONResult and ActionResult?

When to use JSONResult in MVC?

号

ActionResult是操作可以返回的抽象类。

Controller中的辅助方法(如Json()、Content()、View()…)返回继承ActionResult的不同具体类，包括JsonResult。

您应该将您的操作方法声明为返回ActionResult，这样它们就可以自由地返回任何具体的结果类。

当您希望返回客户机(网页或移动客户机上的javascript)使用的原始JSON数据时，请使用JsonResult。

如果您想返回一个由浏览器处理的视图、重定向等，请使用ActionResult。

ActionResult是一个抽象类，JsonResult是ActionResult的子类。所以我们可以返回两种类型的JSON内容。

JsonResult

This one is a bit more complex, but still not very. It also has
hardcoded its ContentType, but what makes it a bit more complex is
that it uses a hardcoded JavaScriptSerializer to serialize the JSON
data before writing it directly to the response.

号

这篇文章很有帮助http://brendan.enrick.com/post/types-of-aspnet-mvc-3-action-results.aspx

根据ActionResult的msdn文件：

The ActionResult class Encapsulates the result of an action method and
is used to perform a framework-level operation on behalf of the action
method.

An action method responds to user input by performing work and
returning an action result. An action result represents a command that
the framework will perform on behalf of the action method. The
ActionResult class is the base class for action results

号

对于jsonresult：

Represents a class that is used to send JSON-formatted content to the
response.

号