Cannot serialize type 'TickDataDefinition.data' because it does not have any serializable fields nor properties

Question

I get this error when I tried to declare the serializer as below. It returns the error which I do not understand what it means.

var serializer = MsgPack.Serialization.MessagePackSerializer.Create<data>();            

Below is the class definition.

using System;
using System.Collections.Generic;
using System.Text;

namespace TickDataDefinition
{
    class data
    {
        private enum type { trade, quote }
        private long time;
        private double bid1;
        private double ask1;
        private double bidsize;
        private double asksize;
        private double price;
        private uint size;
        public data()
        {
        }
        public data(long t, double b, double a, double bs, double ask)
        {
            time = t;
            bid1 = b;
            ask1 = a;
            bidsize = bs;
            asksize = ask;
        }
        public data(long t, double p, uint s)
        {
            time = t;
            price = p;
            size = s;
        }

    }
}

Answer 1

All of the elements of that class are private other than constructors (which can't be serialized anyway, and wouldn't make sense if so). Expose some actually accessible elements and serialize.