DataMember ignored when serializing to JSON

Question

I have added DataMemeber to my object properties to change settings when serializing to JSON, however it is not using them. I have attempted to change the name, as well as emitting default values.

My reason for trying to do this is I want to ignore a property if it is at its default value.

I am attempting to use the Microsoft libraries and not the Newtonsoft ones.

    <DataMember(EmitDefaultValue:=True, IsRequired:=False, Name:="addressTable")> Public Property addressTable() As String
        Get
            Return _AddressTable
        End Get
        Set(ByVal value As String)
            _AddressTable = value
        End Set
    End Property


Public Function gObjToStr(ByVal InputObject As Object) As String

    Dim stream1 As New IO.MemoryStream
    Dim ser As Runtime.Serialization.Json.DataContractJsonSerializer = New Runtime.Serialization.Json.DataContractJsonSerializer(InputObject.GetType)

    ser.WriteObject(stream1, InputObject)
    stream1.Position = 0

    Dim sr As New IO.StreamReader(stream1)
    Dim OutString As String = Nothing

    Return sr.ReadToEnd

End Function

Answer 1

You need to remove the EmitDefaultValue attribute from the Property addressTable.

Basically, EmitDefaultValue tells the serialization engine whether to serialize the default value for a field or property being serialized.

The default value for EmitDefaultValue is true, so even if a property has a default value it would be serialized. As per your requirement, if you need to ignore a property, if it has default value then you need to add attribute EmitDefaultValue to the Property and set the value as false, [DataMember(EmitDefaultValue =false)]. In the code posted above, you have set the EmitDefaultValue = true, hence it is generating the addressTable in Serialization.

Also, IsRequired instructs the serialization engine that the member must be present when reading or deserializing. So you should be careful with usage of both Attributes EmitDefaultValue & IsRequired. The default value for IsRequired = false. So you can't have a combination like EmitDefaultValue=false and IsRequired=true, in this case Serialization engine would throw an exception.