Question

I have a type like this:

[ProtoContract]
class Person {
    [ProtoMember(1)]
    public string Name {get;set:}
    [ProtoMember(2)]
    public int Id {get;set;}
}

Later I realized I need another property Age so added it like:

[ProtoContract]
class Person {
    [ProtoMember(1)]
    public string Name {get;set:}
    [ProtoMember(3)]
    public int Age {get;set;}
    [ProtoMember(2)]
    public int Id {get;set;}
}

But since I am still in development phase, I want to change the Age ProtoMember index from 3 to 2, and update the Id ProtoMember appropriately.

Is there a way to do this easily? Or do I have to create another type temporarily to convert it back and forth until I can serialize it to the right type I want in the updated form?

Answer 1

I assume the issue is migrating old data? If so, then v2 can do this for you; however, I would also be personally included to say “meh, Age is #3, Id stays #2” (I can’t see huge benefits in changing this number).

But as an example for the more general case:

var oldModel = RuntimeTypeModel.Create();
// "false" here means "don't apply the normal rules; I'll tell you what to do"
oldModel.Add(typeof(Person), false).Add("Name", "Id");

var newModel = RuntimeTypeModel.Create();
// "true" here means it will read from the attributes etc
newModel.Add(typeof(Person), true);

// now: load from an old file, and write to a new:
var obj = oldModel.Deserialize(inFile, null, typeof(Person));
newModel.Serialize(outFile, obj);

By having 2 different RuntimeTypeModel instances with different configurations you can apply all sorts of odd translations between data. But again – using this just so that Age is #2 seems massive overkill. Indeed, I would simply make my class:

[ProtoContract]
class Person {
    [ProtoMember(1)]
    public string Name {get;set:}
    [ProtoMember(2)]
    public int Id {get;set;}
    [ProtoMember(3)]
    public int Age {get;set;}
}

And look! They are magically in order!