How to use protobuf-net with immutable value types?

Question

Suppose I have an immutable value type like this:

[Serializable]
[DataContract]
public struct MyValueType : ISerializable
{
private readonly int _x;
private read         


        

Answer 1

Which version of protobuf-net are you using? If you are the latest v2 build, it should cope with this automatically. In case I haven't deployed this code yet, I'll update the download areas in a moment, but essentially if your type is unadorned (no attributes), it will detect the common "tuple" patten you are using, and decide (from the constructor) that x (constructor parameter)/X (property) is field 1, and z/Z is field 2.

Another approach is to mark the fields:

[ProtoMember(1)]
private readonly int _x;

[ProtoMember(2)]
private readonly int _z;

(or alternatively [DataMember(Order=n)] on the fields)

which should work, depending on the trust level. What I haven't done yet is generalise the constructor code to attributed scenarios. That isn't hard, but I wanted to push the basic case first, then evolve it.

I've added the following two samples/tests with full code here:

    [Test]
    public void RoundTripImmutableTypeAsTuple()
    {
        using(var ms = new MemoryStream())
        {
            var val = new MyValueTypeAsTuple(123, 456);
            Serializer.Serialize(ms, val);
            ms.Position = 0;
            var clone = Serializer.Deserialize(ms);
            Assert.AreEqual(123, clone.X);
            Assert.AreEqual(456, clone.Z);
        }
    }
    [Test]
    public void RoundTripImmutableTypeViaFields()
    {
        using (var ms = new MemoryStream())
        {
            var val = new MyValueTypeViaFields(123, 456);
            Serializer.Serialize(ms, val);
            ms.Position = 0;
            var clone = Serializer.Deserialize(ms);
            Assert.AreEqual(123, clone.X);
            Assert.AreEqual(456, clone.Z);
        }
    }

Also:

it turns out that the Serialize method only allows reference types

yes, that was a design limitation of v1 that related to the boxing model etc; this no longer applies with v2.

Also, note that protobuf-net doesn't itself consume ISerializable (although it can be used to implement ISerializable).