C# 之 Ref Out

如下代码：

   static void Main(string[] args)
        {
            Console.WriteLine("Hello World!");
            var (a, b, c) = ("a","b","c");
            myRef(ref a,out b,c);
            Console.WriteLine(a+b+c);
            Console.ReadKey();

        }

        static void myRef(ref string a, out string b, string c)
        {
            a = "aaa";
            b = "bbb";
            c = "ccc";
        }

　　查看IL:

    .method private hidebysig static 
        void Main (
            string[] args
        ) cil managed 
    {
        // Method begins at RVA 0x2050
        // Code size 62 (0x3e)
        .maxstack 3
        .entrypoint
        .locals init (
            [0] string a,
            [1] string b,
            [2] string c
        )

        // (no C# code)
        IL_0000: nop
        // Console.WriteLine("Hello World!");
        IL_0001: ldstr "Hello World!"
        IL_0006: call void [System.Console]System.Console::WriteLine(string)
        // (no C# code)
        IL_000b: nop
        // string a = "a";
        IL_000c: ldstr "a"
        IL_0011: stloc.0
        // string b = "b";
        IL_0012: ldstr "b"
        IL_0017: stloc.1
        // string text = "c";
        IL_0018: ldstr "c"
        IL_001d: stloc.2
        // myRef(ref a, out b, text);
        IL_001e: ldloca.s 0
        IL_0020: ldloca.s 1
        IL_0022: ldloc.2
        IL_0023: call void ConsoleApp1.Program::myRef(string&, string&, string)
        // (no C# code)
        IL_0028: nop
        // Console.WriteLine(a + b + text);
        IL_0029: ldloc.0
        IL_002a: ldloc.1
        IL_002b: ldloc.2
        IL_002c: call string [System.Runtime]System.String::Concat(string, string, string)
        IL_0031: call void [System.Console]System.Console::WriteLine(string)
        // (no C# code)
        IL_0036: nop
        // Console.ReadKey();
        IL_0037: call valuetype [System.Console]System.ConsoleKeyInfo [System.Console]System.Console::ReadKey()
        IL_003c: pop
        // }
        IL_003d: ret
    } // end of method Program::Main

可以看到，这里ref  和Out 用到了指针。

最后将对象引用（类型 O）值存储在给定地址 ，Out 在方法上 多了一个 [out]