LINQ中Aggregate的用法

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

namespace LinqDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            List<TypeEnum> lstTypeEnum = new List<TypeEnum>() { TypeEnum.A,TypeEnum.B,TypeEnum.C };

            var lstType = lstTypeEnum.Aggregate(new List<int>(),
                (total,next) => 
                { 
                    total.Add(((int)next)); 
                    return total; 
                }
            );

            Console.WriteLine(string.Join(",", lstType.ToArray()));//输出1,2,3
            Console.ReadKey();
        }
    }
    public enum TypeEnum
    {
        A = 1,B = 2,C=3
    }
}