WebApi返回Xml和返回json處理方法

webApi可以返回json、xml和自定義string字符串，本文我們不討論返回string字符串。

一、全局都只能返回一種類型Xml或者json

1、返回xml，當我們新建一個webapi項目的時候系統默認webapiConfig默認返回xml此時webapiconfig的配置爲：

 public static void Register(HttpConfiguration config)
        {
            // Web API configuration and services

            // Web API routes
            config.MapHttpAttributeRoutes();

            config.Routes.MapHttpRoute(
                name: "DefaultApi",
                routeTemplate: "api/{controller}/{action}/{id}",
                defaults: new { id = RouteParameter.Optional }
            );


            config.Routes.MapHttpRoute(
                name: "Products",
                routeTemplate: "api/{controller}/{id}",
                defaults: new { id = RouteParameter.Optional }

            );
}

2、當我們需要返回json的時候整個配置文件變爲

 public static class WebApiConfig
    {
        public static void Register(HttpConfiguration config)
        {
            // Web API configuration and services

            // Web API routes
            config.MapHttpAttributeRoutes();

            config.Routes.MapHttpRoute(
                name: "DefaultApi",
                routeTemplate: "api/{controller}/{action}/{id}",
                defaults: new { id = RouteParameter.Optional }
            );


            config.Routes.MapHttpRoute(
                name: "Products",
                routeTemplate: "api/{controller}/{id}",
                defaults: new { id = RouteParameter.Optional }

            );



            var jsonFormatter = new JsonMediaTypeFormatter();
            //optional: set serializer settings here
            config.Services.Replace(typeof(IContentNegotiator), new JsonContentNegotiator(jsonFormatter));
            // 取消註釋下面的代碼行可對具有 IQueryable 或 IQueryable<T> 返回類型的操作啓用查詢支持。
            // 若要避免處理意外查詢或惡意查詢，請使用 QueryableAttribute 上的驗證設置來驗證傳入查詢。


            // 若要在應用程序中禁用跟蹤，請註釋掉或刪除以下代碼行

            //config.EnableSystemDiagnosticsTracing();
        }




        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;
            }
        }
    }

二、需要單個方法返回json，則只是需要在某一個方法中添加json方法。如下：

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; 
} 

封裝返回json方法

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; 
}