How to deserialize generic dictionary with object value in protobuf-net using a proxy/shim property?

Question

I've tried using the solutions in this post. Both the property and the surrogate didn't work. The cause would most likely be that protobuf-net doesn't work on dictionary directly but serializes the types a dictionary contains (and a surrogate on object is impossible).

My test code

class Program

{

    static void Main(string[] args)

    {

        var library = new Library();

        library.Keeper.Add("Harry Potter", "blablabla text... text...");

        library.Keeper.Add("Other book", "Awesome story.");



        // Write and read to test serializing.

        Library deserialize;

        using (var ms = new MemoryStream())

        {

            Serializer.Serialize(ms, library);



            ms.Flush();

            ms.Position = 0;



            deserialize = Serializer.Deserialize<Library>(ms);

        }



        Console.WriteLine(deserialize.Keeper.Count);

    }

}

Library class

[ProtoContract]

public class Library

{

    public Dictionary<string, object> Keeper { get; set; }



    [ProtoMember(1)]

    public Dictionary<string, string> KeeperSer

    {

        get

        {

            var res = new Dictionary<string, string>();

            foreach (var pair in Keeper)

            {

                res.Add(pair.Key, TypeDescriptor.GetConverter(pair.Value.GetType()).ConvertToInvariantString(pair.Value));

            }

            return res;

        }

        set

        {

            var set = new Dictionary<string, object>();

            foreach (var pair in value)

            {

                set.Add(pair.Key, pair.Value);

            }

            Keeper = set;

        }

    }



    public Library()

    {

        Keeper = new Dictionary<string, object>();

    }

}

I've also tried adding [ProtoIgnore] to the

Keeper

property. Adding a breakpoint at the setter of either

KeeperSer

or

Keeper

never triggers when running the project. The getters do work and the data is being written by protobuf-net to the

MemoryStream

. The length also varies when adding new items to the

Library

.

The reason for the

Dictionary<string, object>

is that I'm using

TypeDescriptor.GetConverter(Type)

in another project. And I want to dynamically convert types to my required type.

What am I missing to make the setter of the proxy/shim property

KeeperSer

working?

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Answer 1

Through testing it seems that any IEnumerable<object> compatible type just won't work in any way with Protobuf-net because it doesn't know how to handle it at all. The setter of those types never get called even though no error is thrown. Besides that, using a generic surrogate to 'cheat' the implicit operator gives a recursive loop inside Protobuf-net.

For now, I think I need to go with just storing a textual representation of the object data and never use object in conjunction with the Protobuf-net serializer.

How to deserialize generic dictionary with object value in protobuf-net using a proxy/shim property?

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