LINQ 用法，返回结果不是在定义时取值，而是在调用时实时取值，有意思！

var names = new List<string> { "Nino o", "Alberto", "Juan", "Mike", "phi1" };

            var namesWithJ = from n in names

                             where n.StartsWith("J")

                             orderby n

                             select n;

            Console.WriteLine("First iteration");

            foreach (string name in namesWithJ)

            {

                Console.WriteLine(name);

            }

            Console.WriteLine();

            names.Add("John");

            names.Add("Jim");

            names.Add("Jack");

            names.Add("Denny");

            Console.WriteLine("second iteration");

            foreach (string name in namesWithJ)

            {

                Console.WriteLine(name);

            }

返回结果如下：

First iteration
Juan

second iteration
Jack
Jim
John
Juan

其他情况：

var names = new List<string> { "Nino o", "Alberto", "Juan", "Mike", "phi1" };

            var namesWithJ = (from n in names

                             where n.StartsWith("J")

                             orderby n

                             select n).ToList();

            Console.WriteLine("First iteration");

            foreach (string name in namesWithJ)

            {

                Console.WriteLine(name);

            }

            Console.WriteLine();

            names.Add("John");

            names.Add("Jim");

            names.Add("Jack");

            names.Add("Denny");

            Console.WriteLine("second iteration");

            foreach (string name in namesWithJ)

            {

                Console.WriteLine(name);

            }

返回结果如下：

First iteration
Juan

second iteration

Juan