Generics

using System;
using System.Collections.Generic;
using System.IO;

namespace ConsoleApp5
{
    class Program
    {
        static void Main(string[] args)
        {
            List<BaseData> datas = new List<BaseData>();
            datas.Add(new AData());
            datas.Add(new BData());

            List<BaseData> newData = new List<BaseData>();

            foreach (BaseData data in datas)
            {
                BaseData x = data.Create(data);
            }
        }
    }

    public abstract class BaseData
    {
        public string guid;

        public BaseData()
        {
            guid = string.Empty;
        }

        public BaseData(BaseData data)
        {
            guid = data.guid;
        }

        public abstract BaseData Create<T>(T data) where T : BaseData;

        public T GetBaseData<T>() where T : BaseData
        {
            return this as T;
        }
    }

    public class AData : BaseData
    {
        public string A;

        public AData() : base()
        {
            A = string.Empty;
        }

        public AData(AData data) : base(data)
        {
            A = data.A;
        }

        public override AData Create<T>(T data)
        {
            AData oldData = data.GetBaseData<AData>();
            AData newSuperAData = new AData(oldData);
            return newSuperAData;
        }

    }

    public class BData : BaseData
    {
        public string B;

        public BData() : base()
        {
            B = string.Empty;
        }

        public BData(BData data) : base(data)
        {
            B = data.B;
        }

        public override BData Create<T>(T data)
        {
            BData oldData = data.GetBaseData<BData>();
            BData newSuperBData = new BData(oldData);
            return newSuperBData;
        }
    }

}