Func和Func

TSource和TResult

/*
Func<TResult>和Func<TSource, TResult>
*/

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConAppTRusult
{
    class Program
    {
        static void Main(string[] args)
        {
            var obj = new User();
            obj.TestTResult();
        }
    }


    class User
    {

        public int ID { get; set; }

        public string Name { get; set; }

        public char Sex { get; set; }

        public int Age { get; set; }


        public List<User> GetUser()
        {           

            var list = new List<User>();

            var u1 = new User();
            u1.ID = 1;
            u1.Name = "Alan";
            u1.Sex = 'M';
            u1.Age = 33;
            list.Add(u1);

            var u2 = new User();
            u2.ID = 2;
            u2.Name = "Betty";
            u2.Sex = 'F';
            u2.Age = 31;
            list.Add(u2);

            var u3 = new User();
            u3.ID = 3;
            u3.Name = "Cora";
            u3.Sex = 'F';
            u3.Age = 27;
            list.Add(u3);


            return list;

        }



        public static List<User> GetUserList()
        {
            return new List<User>();
            //return new User().GetUser();
        }

        public static List<User> GetUserListByModel(User model)
        {
            return new List<User>();
            //return new User().GetUser();
        }

        public static TResult GetModelList<TResult>(Func<TResult> GetFunc)
        {
            return default(TResult);
        }
        public static TResult GetModelList<TSource, TResult>(Func<TSource, TResult> GetFunc)
        {
            return default(TResult);
        }

        public static TResult GetModelList2<TResult>(Func<TResult> GetFunc) where TResult : class   //where TResult : List<User>
        {
            //return default(TResult);
            return new User().GetUser() as TResult;
        }
        public static TResult GetModelList2<TSource, TResult>(Func<TSource, TResult> GetFunc) where TResult : List<User>
        {
            //return default(TResult);
            return new User().GetUser() as TResult;
        }


        public void TestTResult()
        {
            GetModelList(GetUserList);
            //GetModelList(GetUserListByModel);
            GetModelList((User User) => GetUserListByModel(User));


            //var list = new User().GetUser();
            //var list = GetUserList();
            //var list = GetModelList(GetUserList);     //error: list is null
            var list = GetModelList2(GetUserList);      //right: list is not null                
            //var list = GetModelList2((User User) => GetUserListByModel(User));//right: list is not null   

            foreach (var item in list)
            {              
                Console.WriteLine(item.ID + "-" + item.Name+"-"+item.Sex+"-"+item.Age);
            }

            //下面語句等價
            //GetModelList2(GetUserList) <=> GetModelList2<List<User>>(GetUserList);
        }

    }
}

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