GlobalConfiguration.Configuration.Formatters.JsonFormatter.MediaTypeMappings.Add(new QueryStringMapping("json", "true", "application/json")); protected void Application_Start() {     AreaRegistration.RegisterAllAreas();     //添加json 解析  使用方法 http://xxx/api/action?json=true     GlobalConfiguration.Configuration.Formatters.JsonFormatter.MediaTypeMappings.Add(new QueryStringMapping("json", "true", "application/json"));     WebApiConfig.Register(GlobalConfiguration.Configuration);     FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);     RouteConfig.RegisterRoutes(RouteTable.Routes);     BundleConfig.RegisterBundles(BundleTable.Bundles); }

GlobalConfiguration.Configuration.Formatters.XmlFormatter.SupportedMediaTypes.Clear(); protected void Application_Start() {     AreaRegistration.RegisterAllAreas();     WebApiConfig.Register(GlobalConfiguration.Configuration);     FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);     RouteConfig.RegisterRoutes(RouteTable.Routes);     BundleConfig.RegisterBundles(BundleTable.Bundles);     //删除xml的解析 当返回值是string 时 直接返回string不是json对象     GlobalConfiguration.Configuration.Formatters.XmlFormatter.SupportedMediaTypes.Clear(); }

System.Web.Extensions public static HttpResponseMessage ToJson(Object obj) {     String str;     if (obj is String || obj is Char)     {         str = obj.ToString();     }     else     {         var serializer = new JavaScriptSerializer();         str = serializer.Serialize(obj);     }     var result = new HttpResponseMessage { Content = new StringContent(str, Encoding.GetEncoding("UTF-8"), "application/json") };     return result; }

public HttpResponseMessage GetString(string name) {      return ToJson(name); }

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;     } }

public static void Register(HttpConfiguration config) {     config.Routes.MapHttpRoute(         name: "DefaultApi",         routeTemplate: "api/{controller}/{id}",         defaults: new { id = RouteParameter.Optional }     );     var jsonFormatter = new JsonMediaTypeFormatter();     config.Services.Replace(typeof(IContentNegotiator), new JsonContentNegotiator(jsonFormatter));     // 取消注释下面的代码行可对具有 IQueryable 或 IQueryable<T> 返回类型的操作启用查询支持。     // 若要避免处理意外查询或恶意查询，请使用 QueryableAttribute 上的验证设置来验证传入查询。     // 有关详细信息，请访问 http://go.microsoft.com/fwlink/?LinkId=279712。     //config.EnableQuerySupport();     // 若要在应用程序中禁用跟踪，请注释掉或删除以下代码行     // 有关详细信息，请参阅: http://www.asp.net/web-api     config.EnableSystemDiagnosticsTracing(); }