namespace ConsoleAppTest
{
    public struct AFS
    {
        public int x; 
        public int y;
        public string Name;
    }
    internal class Program
    {
        static void Main(string[] args)
        {

            List<Com> l = new List<Com>()
            {
                new Com(){id=1,Name="boolive"},
                new Com(){id=2,Name="boolive"}
            };
            List<Com> l1 = new List<Com>()
            {
                new Com(){id=1,Name="boolive"},
                new Com(){id=3,Name="boolive"}
            };
            var DDD= l1.Except(l).ToList();
            var DDD1= l.Except(l1).ToList();




            List<Product> lll = new List<Product>()
            {
                new Product{id=1,ComId=1},
                new Product{id=2,ComId=2},
                new Product{id=3,ComId=3},
            };


            var str = l.Where(s => s.Name.StartsWith("JavaScript")).DefaultIfEmpty().First();
            Console.WriteLine("str=" + str.Name);     //输出空白
            //使用string str1 = ListInt.Where(s => s.StartsWith("JavaScript")).First();  如去掉DefaultEmpty就会报异常               
            Console.WriteLine("Hello, World!");
        }
    }
    public struct Com
    {
        public int id { get; set; }
        public string Name { get; set; }
    }
    public class Product
    {
        public int id { get; set; }
        public int ComId { get; set; }
        public string Name { get; set; }
    }
}