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Json.NET

Conditional Property Serialization

 

Json.NET has the ability to conditionally serialize properties by placing a ShouldSerialize method on a class. This functionality is similar to the XmlSerializer ShouldSerialize feature.

ShouldSerialize

To conditionally serialize a property, add a method that returns boolean with the same name as the property and then prefix the method name with ShouldSerialize. The result of the method determines whether the property is serialized. If the method returns true then the property will be serialized, if it returns false then the property will be skipped.

Employee class with a ShouldSerialize method
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public class Employee
{
    public string Name { get; set; }
    public Employee Manager { get; set; }

    public bool ShouldSerializeManager()
    {
        // don't serialize the Manager property if an employee is their own manager
        return (Manager != this);
    }
}
ShouldSerialize output
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Employee joe = new Employee();
joe.Name = "Joe Employee";
Employee mike = new Employee();
mike.Name = "Mike Manager";

joe.Manager = mike;

// mike is his own manager
// ShouldSerialize will skip this property
mike.Manager = mike;

string json = JsonConvert.SerializeObject(new[] { joe, mike }, Formatting.Indented);
// [
//   {
//     "Name": "Joe Employee",
//     "Manager": {
//       "Name": "Mike Manager"
//     }
//   },
//   {
//     "Name": "Mike Manager"
//   }
// ]
IContractResolver

ShouldSerialize can also be set using an IContractResolver. Conditionally serializing a property using an IContractResolver is useful if you don't want to place a ShouldSerialize method on a class or you didn't declare the class and are unable to.

Conditional properties with IContractResolver
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public class ShouldSerializeContractResolver : DefaultContractResolver
{
    public new static readonly ShouldSerializeContractResolver Instance = new ShouldSerializeContractResolver();

    protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)
    {
        JsonProperty property = base.CreateProperty(member, memberSerialization);

        if (property.DeclaringType == typeof(Employee) && property.PropertyName == "Manager")
        {
            property.ShouldSerialize =
                instance =>
                {
                    Employee e = (Employee)instance;
                    return e.Manager != e;
                };
        }

        return property;
    }
}
See Also