初始化

ConsoleAppTest/Program.cs

@@ -0,0 +1,55 @@
+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; }
+    }
+}