一、如何用AJAX调用JsonResult方法
比如FuckController中添加有个返回JsonResult类型的方法FuckJson()：
复制代码 代码如下:
<span>public<span> <span>JsonResult<span> <span>FuckJson<span>()<span>
<span>{<span>
<span>return<span> <span>new<span> <span>JsonResult<span>()<span>
<span>{<span>
<span>Data<span> <span>=<span> <span>new<span> <span>List<span><string><span>()<span> <span>{<span> <span>"fuck"<span>,<span> <span>"shit"<span> <span>},<span> <span>JsonRequestBehavior<span> <span>=<span> <span>JsonRequestBehavior<span>.<span>AllowGet<span>
<span>};<span>
<span>}</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span>
如果我们直接在浏览器里调用，是可以看到结果的：
因为在浏览器地址栏直接输入这个地址，是一次GET请求，这就是为毛上面的代码里要写JsonRequestBehavior.AllowGet。
用JQuery AJAX调用的代码如下：
复制代码 代码如下:
<span>$<span>.<span>ajax<span>({<span>
url<span>:<span> <span>"/Fuck/FuckJson"<span>,<span>
data<span>:<span> <span>""<span>,<span>
dataType<span>:<span> <span>"json"<span>,<span>
type<span>:<span> <span>"POST"<span>,<span>
contentType<span>:<span> <span>"application/json; charset=utf-8"<span>,<span>
dataFilter<span>:<span> <span>function<span> <span>(<span>data<span>)<span> <span>{<span>
<span>return<span> data<span>;<span>
<span>},<span>
success<span>:<span> <span>function<span> <span>(<span>data<span>)<span> <span>{<span>
alert<span>(<span>data<span>);<span>
<span>}<span>
<span>})</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span>
url: "/Fuck/FuckJson" 很显然是Action的位置。data: "" 表示FuckJson()放方没有参数。dataType: "json"是理所当然的，我们返回的就是JsonResult。
二、返回自定义错误消息
默认情况下，如果AJAX请求发生了错误。它最多只知道错误码，而无法显示具体的错误信息。但报错通常是需要的，所以我们先要写一个过滤器，作用是一旦发生exception，就给返回的json中的data属性加一个errorMessage。并且，response的状态不能是200，不然ajax请求会以为没有发生错误。一般的服务器端错误代码是500。这个过滤器函数如下：
复制代码 代码如下:
<span>public<span> <span>class<span> <span>JsonExceptionFilterAttribute<span> <span>:<span> <span>FilterAttribute<span>,<span> <span>IExceptionFilter<span>
<span>{<span>
<span>public<span> <span>void<span> <span>OnException<span>(<span>ExceptionContext<span> filterContext<span>)<span>
<span>{<span>
<span>if<span> <span>(<span>filterContext<span>.<span>RequestContext<span>.<span>HttpContext<span>.<span>Request<span>.<span>IsAjaxRequest<span>())<span>
<span>{<span>
filterContext<span>.<span>HttpContext<span>.<span>Response<span>.<span>StatusCode<span> <span>=<span> <span>500<span>;<span>
filterContext<span>.<span>ExceptionHandled<span> <span>=<span> <span>true<span>;<span>
filterContext<span>.<span>Result<span> <span>=<span> <span>new<span> <span>JsonResult<span>
<span>{<span>
<span>Data<span> <span>=<span> <span>new<span>
<span>{<span>
errorMessage <span>=<span> filterContext<span>.<span>Exception<span>.<span>Message<span>
<span>},<span>
<span>JsonRequestBehavior<span> <span>=<span> <span>JsonRequestBehavior<span>.<span>AllowGet<span>
<span>};<span>
<span>}<span>
<span>}<span>
<span>}</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span>
之后，我们要给FuckJson()方法加上这个“特征”（Attribute在C#中最好不要翻译为属性），然后故意抛个错做测试。修改后的方法如下：
复制代码 代码如下:
<span>[<span>JsonExceptionFilterAttribute<span>]<span>
<span>public<span> <span>JsonResult<span> <span>FuckJson<span>()<span>
<span>{<span>
<span>try<span>
<span>{<span>
<span>throw<span> <span>new<span> <span>Exception<span>(<span>"oh shit!"<span>);<span>
<span>return<span> <span>new<span> <span>JsonResult<span>()<span>
<span>{<span>
<span>Data<span> <span>=<span> <span>new<span> <span>List<span><string><span>()<span> <span>{<span> <span>"fuck"<span>,<span> <span>"shit"<span> <span>},<span> <span>JsonRequestBehavior<span> <span>=<span> <span>JsonRequestBehavior<span>.<span>AllowGet<span>
<span>};<span>
<span>}<span>
<span>catch<span> <span>(<span>Exception<span> ex<span>)<span>
<span>{<span>
<span>throw<span> ex<span>;<span>
<span>}<span>
<span>}</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span>
捕获异常后，你也可以先记一下log、或是根据你自己的需要处理一下这个异常，然后再throw。
最后我们的AJAX请求代码也得做修改，增加一个error的处理：
复制代码 代码如下:
<span>$<span>.<span>ajax<span>({<span>
url<span>:<span> <span>"/Fuck/FuckJson"<span>,<span>
data<span>:<span> <span>""<span>,<span>
dataType<span>:<span> <span>"json"<span>,<span>
type<span>:<span> <span>"POST"<span>,<span>
contentType<span>:<span> <span>"application/json; charset=utf-8"<span>,<span>
dataFilter<span>:<span> <span>function<span> <span>(<span>data<span>)<span> <span>{<span>
<span>return<span> data<span>;<span>
<span>},<span>
success<span>:<span> <span>function<span> <span>(<span>data<span>)<span> <span>{<span>
alert<span>(<span>data<span>);<span>
<span>},<span>
error<span>:<span> <span>function<span> <span>(<span>fuckedObject<span>)<span> <span>{<span>
<span>try<span> <span>{<span>
<span>var<span> json <span>=<span> $<span>.<span>parseJSON<span>(<span>fuckedObject<span>.<span>responseText<span>);<span>
alert<span>(<span>json<span>.<span>errorMessage<span>);<span>
<span>}<span> <span>catch<span>(<span>e<span>)<span> <span>{<span>
alert<span>(<span>'something bad happened'<span>);<span>
<span>}<span>
<span>}<span>
<span>})</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span>
现在请求这个Action，会发现Response的状态已经是500了。并且返回了Json格式的错误信息。