What is opt in serializer

Question

I am learning wcf, and I am seeing this opt in and opt out serialization. I am still scratching my head. I have already seen this SO post. But it didn't help. Can someone explain me succinctly what it is?

Answer 1

actually its so simple: Opt-In approach says properties that are considered to be part of DataContract must be explicitly marked othewise will be ignore, while Opt-Out means all of the properties will be assumed to be part of the DataContract unless marked explicitly.

namespace MySchoolService

    {
                    [DataContract]
                    public class Student
                   {
                           [DataMember]
                           public string StudentNumber;
                           [DataMember]
                           public string FirstName;
                           [DataMember]
                           public string LastName;                     

                          public string MarksObtained;
                   }
                  [ServiceContract]
                   public interface IStudentService
                   {
                              //Service Code Here.
                   }
    }

In above code StudentNumber, FirstName, LastName properties of Student class are explicitly marked with DataMember attribute as oppose to MarksObtained, so MarksObtained will be ignored. Below code represents an example of Opt-Out approach.

namespace MySchoolService
{
                [Serializable()]
                public class Student
               {
                       public string StudentNumber;
                       public string FirstName;
                       public string LastName;                     
                      [NonSerialized()]
                      public string marksObtained;
               }               
               [ServiceContract]
               public interface IStudentService
               {
                          //Service Code Here.
               }
}

In above example, we explicitly marked MarksObtained property as [NonSerialized()] attribute, so it will be ignored except the others. hope could help you.