prevent property from being serialized in web API

Question

I m using an MVC 4 web API and asp net web forms 4 0 to build a rest API  It s working great    HttpGet  public HttpResponseMessage Me string hash        HttpResponseMessage httpResponseMessage      List lt Something gt  somethings            httpResponseMessage   Request CreateResponse HttpStatusCode OK                                    new   result   true  somethings   somethings          return httpResponseMessage      Now I need to prevent some properties to be serialized  I know I can use some LINQ over the list and get only the properties I need  and generally it s a good approach  but in the present scenario the something object is too complex  and I need a different set of properties in different methods  so it s easier to mark  at runtime  each property to be ignored   Is there a way to do that

User · Answer

I will show you 2 ways to accomplish what you want:

First way: Decorate your field with JsonProperty attribute in order to skip the serialization of that field if it is null.

public class Foo
{
    public int Id { get; set; }
    public string Name { get; set; }

    [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
    public List<Something> Somethings { get; set; }
}

Second way: If you are negotiation with some complex scenarios then you could use the Web Api convention ("ShouldSerialize") in order to skip serialization of that field depending of some specific logic.

public class Foo
{
    public int Id { get; set; }
    public string Name { get; set; }

    public List<Something> Somethings { get; set; }

    public bool ShouldSerializeSomethings() {
         var resultOfSomeLogic = false;
         return resultOfSomeLogic; 
    }
}

WebApi uses JSON.Net and it use reflection to serialization so when it has detected (for instance) the ShouldSerializeFieldX() method the field with name FieldX will not be serialized.

User · Answer

ASP NET Web API uses Json Net as default formatter  so if your application just only uses JSON as data format  you can use  JsonIgnore  to ignore property for serialization   public class Foo       public int Id   get  set        public string Name   get  set          JsonIgnore      public List lt Something gt  Somethings   get  set        But  this way does not support XML format  So  in case your application has to support XML format more  or only support XML   instead of using Json Net  you should use  DataContract  which supports both JSON and XML    DataContract  public class Foo        DataMember      public int Id   get  set         DataMember      public string Name   get  set           Ignore by default     public List lt Something gt  Somethings   get  set        For more understanding  you can read the official article

User · Answer

For  NET Core 3 0 and above   The default JSON serializer for ASP NET Core is now System Text Json  which is new in  NET Core 3 0  Consider using System Text Json when possible  It s high-performance and doesn t require an additional library dependency   https   docs microsoft com en-us aspnet core migration 22-to-30 view aspnetcore-3 1 amp tabs visual-studio newtonsoftjson-jsonnet-support Sample  Thanks cuongle  using System Text Json Serialization   public class Foo       public int Id   get  set        public string Name   get  set          JsonIgnore      public List lt Something gt  Somethings   get  set       If you already have Newtonsoft Json intalled and chose to use it instead  by default   JsonIgnore  won t work as expected

User · Answer

Try using IgnoreDataMember property  public class Foo                IgnoreDataMember          public int Id   get  set            public string Name   get  set

User · Answer

Works fine by just adding the   IgnoreDataMember   On top of the propertyp  like   public class UserSettingsModel       public string UserName   get  set         IgnoreDataMember      public DateTime Created   get  set        This works with ApiController  The code    Route  api Context UserSettings         HttpGet  HttpPost      public UserSettingsModel UserSettings                 return  contextService GetUserSettings

User · Answer

This worked for me  Create a custom contract resolver which has a public property called AllowList of string array type  In your action  modify that property depending on what the action needs to return   1  create a custom contract resolver   public class PublicDomainJsonContractResolverOptIn   DefaultContractResolver       public string   AllowList   get  set         protected override IList lt JsonProperty gt  CreateProperties Type type  MemberSerialization memberSerialization                IList lt JsonProperty gt  properties   base CreateProperties type  memberSerialization            properties   properties Where p   gt  AllowList Contains p PropertyName   ToList            return properties            2  use custom contract resolver in action   HttpGet  public BinaryImage Single int key          limit properties that are sent on wire for this request specifically     var contractResolver   Configuration Formatters JsonFormatter SerializerSettings ContractResolver as PublicDomainJsonContractResolverOptIn      if  contractResolver    null          contractResolver AllowList   new string      Id    Bytes    MimeType    Width    Height          BinaryImage image   new BinaryImage   Id   1          etc  etc      return image      This approach allowed me to allow disallow for specific request instead of modifying the class definition  And if you don t need XML serialization  don t forget to turn it off in your App Start WebApiConfig cs or your API will return blocked properties if the client requests xml instead of json     remove xml serialization var appXmlType   config Formatters XmlFormatter SupportedMediaTypes FirstOrDefault t   gt  t MediaType     application xml    config Formatters XmlFormatter SupportedMediaTypes Remove appXmlType

User · Answer

According to the Web API documentation page JSON and XML Serialization in ASP NET Web API to explicitly prevent serialization on a property you can either use  JsonIgnore  for the Json serializer or  IgnoreDataMember  for the default XML serializer   However in testing I have noticed that  IgnoreDataMember  prevents serialization for both XML and Json requests  so I would recommend using that rather than decorating a property with multiple attributes

User · Answer

Almost same as greatbear302 s answer  but i create ContractResolver per request   1  Create a custom ContractResolver  public class MyJsonContractResolver   DefaultContractResolver       public List lt Tuple lt string  string gt  gt  ExcludeProperties   get  set         protected override JsonProperty CreateProperty MemberInfo member  MemberSerialization memberSerialization                JsonProperty property   base CreateProperty member  memberSerialization            if  ExcludeProperties  FirstOrDefault              s   gt  s Item2    member Name  amp  amp  s Item1    member DeclaringType Name     null                        property ShouldSerialize   instance   gt    return false                        return property            2  Use custom contract resolver in action  public async Task lt IActionResult gt  Sites         var items   await db Sites GetManyAsync         return Json items ToList    new JsonSerializerSettings               ContractResolver   new MyJsonContractResolver                         ExcludeProperties   new List lt Tuple lt string  string gt  gt                                Tuple Create  Site    Name                    Tuple Create   lt TypeName gt      lt MemberName gt                                         Edit   It didn t work as expected isolate resolver per request   I ll use anonymous objects   public async Task lt IActionResult gt  Sites         var items   await db Sites GetManyAsync         return Json items Select s   gt  new               s ID          s DisplayName          s Url          UrlAlias   s Url          NestedItems   s NestedItems Select ni   gt  new                       ni Name              ni OrdeIndex              ni Enabled

User · Answer

For some reason  IgnoreDataMember  does not always work for me  and I sometimes get StackOverflowException  or similar   So instead  or in addition  i ve started using a pattern looking something like this when POSTing in Objects to my API    Route  api myroute     AcceptVerbs  POST    public IHttpActionResult PostMyObject JObject myObject        MyObject myObjectConverted   myObject ToObject lt MyObject gt            Do some stuff with the object      return Ok myObjectConverted       So basically i pass in an JObject and convert it after it has been recieved to aviod problems caused by the built-in serializer that sometimes cause an infinite loop while parsing the objects   If someone know a reason that this is in any way a bad idea  please let me know   It may be worth noting that it is the following code for an EntityFramework Class-property that causes the problem  If two classes refer to each-other     Serializable  public partial class MyObject       IgnoreDataMember     public MyOtherObject MyOtherObject   gt  MyOtherObject GetById MyOtherObjectId       Serializable  public partial class MyOtherObject       IgnoreDataMember     public List lt MyObject gt  MyObjects   gt  MyObject GetByMyOtherObjectId Id

User · Answer

Instead of letting everything get serialized by default  you can take the  opt-in  approach  In this scenario  only the properties you specify are allowed to be serialized  You do this with the DataContractAttribute and DataMemberAttribute  found in the System Runtime Serialization namespace   The DataContactAttribute is applied to the class  and the DataMemberAttribute is applied to each member you want to be serialized    DataContract  public class MyClass       DataMember    public int Id   get  set      Serialized     DataMember    public string Name   get  set       Serialized    public string DontExposeMe   get  set       Will not be serialized     Dare I say this is a better approach because it forces you to make explicit decisions about what will or will not make it through serialization  It also allows your model classes to live in a project by themselves  without taking a dependency on JSON net just because somewhere else you happen to be serializing them with JSON net

User · Answer

I m late to the game  but an anonymous objects would do the trick    HttpGet  public HttpResponseMessage Me string hash        HttpResponseMessage httpResponseMessage      List lt Something gt  somethings            var returnObjects   somethings Select x   gt  new           Id   x Id          OtherField   x OtherField              httpResponseMessage   Request CreateResponse HttpStatusCode OK                                    new   result   true  somethings   returnObjects          return httpResponseMessage

User · Answer

You might be able to use AutoMapper and use the  Ignore   mapping and then send the mapped object  CreateMap lt Foo  Foo gt    ForMember x   gt  x Bar  opt   gt  opt Ignore

[c#] prevent property from being serialized in web API

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