web api写api接口时默认返回的是把你的东西序列化后以XML形式返回，那么怎样才华让其返回为json呢，下面就介绍两种要领：
要领一：(改配置法)
找到Global.asax文件，在Application_Start()要领中添加一句：
GlobalConfiguration.Configuration.Formatters.XmlFormatter.SupportedMediaTypes.Clear();
或
GlobalConfiguration.Configuration.Formatters.JsonFormatter.SupportedMediaTypes.Add(new System.Net.Http.Headers.MediaTypeHeaderValue("text/html"));
改削后：
protected void Application_Start() { AreaRegistration.RegisterAllAreas(); WebApiConfig.Register(GlobalConfiguration.Configuration); FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters); RouteConfig.RegisterRoutes(RouteTable.Routes); // 使api返回为json
//GlobalConfiguration.Configuration.Formatters.JsonFormatter.SupportedMediaTypes.Add(new System.Net.Http.Headers.MediaTypeHeaderValue("text/html")); GlobalConfiguration.Configuration.Formatters.XmlFormatter.SupportedMediaTypes.Clear(); }
这样返回的功效就都是json类型了，但有个欠好的处所，如果返回的功效是String类型，如123，返回的json就会酿成"123";
解决的要领是自界说返回类型(返回类型为HttpResponseMessage)
public HttpResponseMessage PostUserName(User user) { String userName = user.userName; HttpResponseMessage result = new HttpResponseMessage { Content = new StringContent(userName,Encoding.GetEncoding("UTF-8"), "application/json") }; return result; }
要领二：(万金油法)
要领一中又要改配置，又要措置惩罚惩罚返回值为String类型的json，甚是麻烦，不如就不用web
api中的的自动序列化东西，本身序列化后再返回
public HttpResponseMessage PostUser(User user) { JavaScriptSerializer serializer = new JavaScriptSerializer(); string str = serializer.Serialize(user); HttpResponseMessage result = new HttpResponseMessage { Content = new StringContent(str, Encoding.GetEncoding("UTF-8"), "application/json") }; return result; }
要领二是我对照保举的要领，为了不在每个接口中都重复写那几句代码，所以就封装为一个要领这样使用就便利多了。
public static HttpResponseMessage toJson(Object obj) { String str; if (obj is String ||obj is Char) { str = obj.ToString(); } else { JavaScriptSerializer serializer = new JavaScriptSerializer(); str = serializer.Serialize(obj); } HttpResponseMessage result = new HttpResponseMessage { Content = new StringContent(str, Encoding.GetEncoding("UTF-8"), "application/json") }; return result; }
要领三：(最麻烦的要领)
要领一最简单，但杀伤力太大，所有的返回的xml格局城市被毙失，那么要领三就可以只让api接口中毙失xml，返回json
先写一个措置惩罚惩罚返回的类：
public class JsonContentNegotiator : IContentNegotiator { private readonly JsonMediaTypeFormatter _jsonFormatter; public JsonContentNegotiator(JsonMediaTypeFormatter formatter) { _jsonFormatter = formatter; } public ContentNegotiationResult Negotiate(Type type, HttpRequestMessage request, IEnumerable<MediaTypeFormatter> formatters) { var result = new ContentNegotiationResult(_jsonFormatter, new MediaTypeHeaderValue("application/json")); return result; } }
找到App_Start中的WebApiConfig.cs文件，打开找到Register(HttpConfiguration config)要领
添加以下代码：
var jsonFormatter = new JsonMediaTypeFormatter(); config.Services.WordStr(typeof(IContentNegotiator), new JsonContentNegotiator(jsonFormatter));
添加儿女码如下：