C# Serialization Issue - DataContractSerializer Not Handling Nullable Types Correctly in .NET 6
I've been banging my head against this for hours. I'm encountering an issue when using `DataContractSerializer` to serialize an object that contains nullable types in .NET 6. Specifically, when serializing an object with a nullable property, the serializer seems to ignore it entirely if the value is `null`. For instance, consider the following class: ```csharp [DataContract] public class Person { [DataMember] public string Name { get; set; } [DataMember] public int? Age { get; set; } } ``` When I create an instance of `Person` like this: ```csharp var person = new Person { Name = "Alice", Age = null }; var serializer = new DataContractSerializer(typeof(Person)); using (var stream = new MemoryStream()) { serializer.WriteObject(stream, person); string xml = Encoding.UTF8.GetString(stream.ToArray()); Console.WriteLine(xml); } ``` The generated XML output ends up excluding the `Age` property completely if it's `null`, resulting in: ```xml <Person> <Name>Alice</Name> </Person> ``` I was expecting to see something like this instead: ```xml <Person> <Name>Alice</Name> <Age xsi:nil="true" /> </Person> ``` I've tried setting the `EmitTypeInformation` on the `DataContractSerializer` to `Always`, but that doesn't seem to help either. Here is what I tried: ```csharp var serializer = new DataContractSerializer(typeof(Person), new DataContractSerializerSettings { EmitTypeInformation = EmitTypeInformation.Always }); ``` However, the output remains unchanged. Is there a specific setting or workaround to ensure that nullable properties are included in the XML output, even when they are `null`? Any guidance would be greatly appreciated!