引用传参

using System;public class Program
{public static void Main(){Tools t = new Tools();t.bf();double a = 10;double b = 20;t.change(ref a, ref b);Console.WriteLine(b);}
}class Tools {public void af() {Console.Write("a\n");}internal void bf() {Console.Write("b\n");}public void change(ref double a, ref double b) {dynamic t;t = a;a = b;b = t;}}

调用方法时，你必须使用 ref 关键字：

t.change(ref a, ref b);

输出传参

using System;namespace LHJ {class TODO {static void Main() {Tools t = new Tools();int a, b;Console.WriteLine("add = {0}, doublea = {1}, double b = {2}",t.foo(2, 3, out a, out b), a, b);}}class Tools {public int foo(int x, int y, out int a, out int b) {a = x * 2;b = y * 2;return x + y;}}}

public int foo(int x, int y, out int a, out int b)

此方法返回一个int的foo，和两个out int
注意调用时要带out

t.foo(2, 3, out a, out b)