SomeGist

Example.cs

    public interface IBuilder<T> where T : PurchaseDocuments
    {
        Entity Build(T dto);
    }

    public abstract class BuilderBase<T> : IBuilder<T> where T : PurchaseDocuments
    {
        public Entity Build(T dto)
        {
            var entity = new Entity();
            var purchaser = GetPurchaser(dto);

            return entity;
        }

        protected abstract PurchaserInfo GetPurchaser(T dto);
    }

    public class ConcreteBuilder : BuilderBase<EokCancellation>
    {
        /// <inheritdoc />
        protected override PurchaserInfo GetPurchaser(EokCancellation dto)
        {
            return dto.Purchaser;
        }
    }