LINQ SelectMany Method in C#-526互联

1.例子一：

   static void SelectMany()
        {
            //方式一：Query Syntax
            Console.WriteLine("方式一：Query Syntax");
            List<string> nameList = new List<string>() { "Kate", "Hanna" };
            IEnumerable<char> methodSyntax = nameList.SelectMany(x => x);
            foreach(char c in methodSyntax)
            {
                Console.Write(c + " ");
            }
            Console.WriteLine("");
            //方式二：Method Syntax:
            Console.WriteLine("方式二：Method Syntax");
            IEnumerable<char> querySyntax = from str in nameList
                                            from ch in str
                                            select ch;
            foreach (char c in querySyntax)
            {
                Console.Write(c + " ");
            }

            Console.ReadKey();
        }

测试结果如下：

2.例子二：

1）先构造数据：

    public class Student2
    {
        public int ID { get; set; }
        public string Name { get; set; }
        public string Email { get; set; }
        public List<string> Programming { get; set; }
        public static List<Student2> GetStudents()
        {
            return new List<Student2>()
            {
                new Student2(){ID = 1, Name = "James", Email = "James@j.com", Programming = new List<string>() { "C#", "Jave", "C++"} },
                new Student2(){ID = 2, Name = "Sam", Email = "Sara@j.com", Programming = new List<string>() { "WCF", "SQL Server", "C#" }},
                new Student2(){ID = 3, Name = "Patrik", Email = "Patrik@j.com", Programming = new List<string>() { "MVC", "Jave", "LINQ"} },
                new Student2(){ID = 4, Name = "Sara", Email = "Sara@j.com", Programming = new List<string>() { "ADO.NET", "C#", "LINQ" } }
            };
        }
    }

2）代码如下：

 static void SelectManyExp2()
        {
            //方式一：Query Syntax
            Console.WriteLine("方式一：Query Syntax");
            IEnumerable<string> QuerySyntax = from std in Student2.GetStudents()
                                              from program in std.Programming
                                              select program;
            //Printing the values
            foreach (string program in QuerySyntax)
            {
                Console.WriteLine(program);
            }

            //方式二：Method Syntax
            Console.WriteLine("方式二：Method Syntax");
            List<string> MethodSyntax = Student2.GetStudents().SelectMany(std => std.Programming).ToList();
            //Printing the values
            foreach (string program in MethodSyntax)
            {
                Console.WriteLine(program);
            }
        }

3）测试结果如下：

这边夹杂着自己的疑问，Select与SelectMany的区别在哪？做如下试验：

 static void SelectVSSelectMany()
        {
            //方式一：Query Syntax
            Console.WriteLine("方式一：Query Syntax");
            var QuerySyntax = from std in Student2.GetStudents()
                              select std.Programming;
            //Printing the values
            foreach (List<string> program in QuerySyntax)
            {
                Console.WriteLine(program);
            }

            //方式二：Method Syntax
            Console.WriteLine("方式二：Method Syntax");
            var MethodSyntax = Student2.GetStudents().Select(std => std.Programming);
            //Printing the values
            foreach (List<string> program in MethodSyntax)
            {
                Console.WriteLine(program);
            }
        }