Protobuf-net: cannot serialize type data, how can I determine type data with protocol buffers?

I am trying to create a simple grid in memory that can be serialized using protocol buffers.

The idea is that the user can create / define columns of any type (primitives or user-defined definitions, if they are protocol buffers).

My problem is that you cannot serialize type data with protocol buffers, so how can I achieve this?

The code below shows how I was hoping to encode the grid columns.

Many thanks.

[TestClass]
public class UnitTest1
{
    [TestMethod]
    public void TestMethod1()
    {
        Column colOrderId = new Column("OrderId", typeof(uint));
        Column colOrderDesc = new Column("OrderDesc", typeof(string));
        Column colPrice = new Column("Price", typeof(Price));
        Column colOrderDateTime = new Column("OrderDateTime", typeof(DateTime));

        var s = colOrderId.ToBArray();
    }
}

[ProtoContract, Serializable]
public sealed class Column
{
    public Column(string name, Type type)
    {
        Name = name;
        Type = type;
    }

    [ProtoMember(1)]
    public string Name { get; private set; }

    [ProtoMember(2)]
    public Type Type { get; private set; }
}

[ProtoContract, Serializable]
public sealed class Price
{
    public Price(double value, string currency)
    {
        Value = value;
        Currency = currency;
    }

    [ProtoMember(1)]
    public double Value { get; private set; }

    [ProtoMember(2)]
    public string Currency { get; private set; }
}

public static class ProtoBufEx
{
    public static byte[] ToBArray<T>(this T o)
    {
        using (MemoryStream ms = new MemoryStream())
        {
            ProtoBuf.Serializer.Serialize(ms, o);
            return ms.ToArray();
        }
    }
}