Struct與賦值

    using System;    using System.Collections.Generic;    struct SomeStruct    {        public int SomeValue;    }    class SomeContainerClass    {        public SomeStruct Struct;    }    struct SomeContainerStruct    {        public SomeStruct Struct;    }    class Program    {        static void Main()        {            TestStruct();            TestClass();            TestArray();            TestList();            Console.ReadKey();        }        static SomeStruct GetDefaultValue()        {            return new SomeStruct { SomeValue = 100 };        }        private static void TestStruct()        {            ShowTestName("TestStruct:");            var c = new SomeContainerStruct { Struct = GetDefaultValue() };            ShowResult("original:", c.Struct.SomeValue);            var s = c.Struct;            s.SomeValue = 200;            ShowResult("indirectly:", c.Struct.SomeValue);            c.Struct.SomeValue = 300;            ShowResult("directly:", c.Struct.SomeValue);        }        private static void TestClass()        {            ShowTestName("TestClass:");            var c = new SomeContainerClass { Struct = GetDefaultValue() };            ShowResult("original:", c.Struct.SomeValue);            var s = c.Struct;            s.SomeValue = 200;            ShowResult("indirectly:", c.Struct.SomeValue);            c.Struct.SomeValue = 300;            ShowResult("directly:", c.Struct.SomeValue);        }        private static void TestArray()        {            ShowTestName("TestArray:");            var c = new[] { GetDefaultValue() };            ShowResult("original:", c[0].SomeValue);            var s = c[0];            s.SomeValue = 200;            ShowResult("indirectly:", c[0].SomeValue);            c[0].SomeValue = 300;            ShowResult("directly:", c[0].SomeValue);        }        private static void TestList()        {            ShowTestName("TestList:");            var c = new List<SomeStruct> { GetDefaultValue() };            ShowResult("original:", c[0].SomeValue);            var s = c[0];            s.SomeValue = 200;            ShowResult("indirectly:", c[0].SomeValue);            //the follow line won't compile            //Cannot modify the return value of 'System.Collections.Generic.List<StructTest.SomeStruct>.this[int]' because it is not a variable            //c[0].SomeValue = 300;            //ShowTestName("directly:", c[0].SomeValue);        }        static void ShowResult(string condition, int value)        {            Console.Write(condition);            Console.Write("\t");            Console.WriteLine(value);        }        static void ShowTestName(string message)        {            Console.WriteLine();            Console.WriteLine(message);        }    }