防止在WebAPI OData v4服务中发出空值

Question

我正在运行WebAPI OData v4服务，并且我不希望发出空值。例如，当我请求User对象，以下则返回：

"value": [ 
{ 
    "FirstName": "John", 
    "LastName": "Smith", 
    "EmailAddress": "john@smith.com", 
    "PasswordHash": null, 
    "PhoneNumber": "11234567890", 
    "Website": null, 
    "Id": "dac9706a-8497-404c-bb5a-ca1024cf213b" 
} 

由于PasswordHash和Website字段是空值，我希望他们不包括在输出中。我试着在应用程序的注册块以下行，但他们没有工作：

config.Formatters.JsonFormatter.SerializerSettings = new JsonSerializerSettings { NullValueHandling = NullValueHandling.Ignore }; 
config.Formatters.JsonFormatter.SerializerSettings.DefaultValueHandling = DefaultValueHandling.IgnoreAndPopulate; 
config.Formatters.JsonFormatter.SerializerSettings.NullValueHandling = NullValueHandling.Ignore; 

下面是注册方法的全部内容。我正在使用Newtonsoft Json包来处理JSON序列化。

public static void Register(HttpConfiguration config) 
    { 
     // Web API configuration and services 
     config.SuppressDefaultHostAuthentication(); 
     config.Filters.Add(new HostAuthenticationFilter(OAuthDefaults.AuthenticationType)); 

     // Web API routes 
     config.MapHttpAttributeRoutes(); 

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

     config.Routes.MapHttpRoute(
      name: "UploadComplete", 
      routeTemplate: "UploadFiles/Complete", 
      defaults: new { controller = "UploadFiles", action = "Complete" } 
     ); 

     var builder = new ODataConventionModelBuilder(); 

     builder.EntitySet<Address>("Addresses"); 
     builder.EntitySet<Assignment>("Assignments"); 
     builder.EntitySet<Course>("Courses"); 
     builder.EntitySet<File>("Files"); 
     builder.EntitySet<UploadFile>("UploadFiles"); 
     builder.EntitySet<Organization>("Organizations"); 
     builder.EntitySet<Submission>("Submissions"); 
     builder.EntitySet<Term>("Terms"); 
     builder.EntitySet<User>("Users"); 

     config.MapODataServiceRoute(
      routeName: "ODataRoute", 
      routePrefix: null, 
      model: builder.GetEdmModel()); 

     // Neither of these lines work. 
     config.Formatters.JsonFormatter.SerializerSettings = new JsonSerializerSettings { NullValueHandling = NullValueHandling.Ignore }; 
     config.Formatters.JsonFormatter.SerializerSettings.DefaultValueHandling = DefaultValueHandling.IgnoreAndPopulate; 
     config.Formatters.JsonFormatter.SerializerSettings.NullValueHandling = NullValueHandling.Ignore; 
    } 

Answer 1

感谢布赖恩罗杰斯指着我在正确的方向，我结束了覆盖ODataEntityTypeSerializer像这样：

public override ODataEntry CreateEntry(SelectExpandNode selectExpandNode, EntityInstanceContext entityInstanceContext) 
{ 
    ODataEntry entry = base.CreateEntry(selectExpandNode, entityInstanceContext); 

    // Remove any properties which are null. 
    List<ODataProperty> properties = new List<ODataProperty>(); 
    foreach (ODataProperty property in entry.Properties) 
    { 
     if (property.Value != null) 
     { 
      properties.Add(property); 
     } 
    } 

    entry.Properties = properties; 
    return entry; 
} 

然后我用代码RaghuRam-Nadiminti's answer实现CustomSerializerProvider类然后我可以在Register使用。

Answer 2

尽管Web API iteself使用Json.Net串行器，该MediaTypeFormatter for Web API OData使用其自己的内部串行这是不 Json.Net。因此，更改配置中的Json.Net序列化程序设置不会对OData产生任何影响。但是，看起来你可以实现你自己的ODataSerializerProvider和ODataDeserializerProvider类来让OData使用Json.Net。请参阅JSON.NET as a WebAPI 2 OData serializer vs ODataMediaTypeFormatter作为起点。