C# - 通过对构造函数的引用传递参数，然后从方法中使用它们

Question

在下面的代码中，我试图让类 TestClass 中的方法 (Work) 更改主程序中某些变量的值，而不必返回它们。变量在 TestClass 构造函数中通过引用传递。

class Program
{
    static void Main(string[] args)
    {
        int a, b, c, d;
        a = 5; b = 10; c = 20; d = 25;
        Console.WriteLine("Main before TestClass: a=" + a + " b=" + b + " c=" + c + " d=" + d);
        TestClass testObj = new TestClass(ref a,ref b,ref c,ref d);
        testObj.Work();
        Console.WriteLine("Main after TestClass: a=" + a + " b=" + b + " c=" + c + " d=" + d);
        Console.ReadLine();
    }
}

public class TestClass
{
    int _a, _b, _c, _d;
    public TestClass(ref int a, ref int b, ref int c, ref int d)
    {
        _a = a; _b = b; _c = c; _d = d;
    }

    public void Work()
    {
        Console.WriteLine("Work before changing: a=" + _a + " b=" + _b + " c=" + _c + " d=" + _d);
        _a = 0; _b = 1; _c = 2; _d = 3;
        Console.WriteLine("Work after changing: a=" + _a + " b=" + _b + " c=" + _c + " d=" + _d);
    }
}

但是这段代码返回:

Main before TestClass: a=5 b=10 c=20 d=25
Work before changing: a=5 b=10 c=20 d=25
Work after changing: a=0 b=1 c=2 d=3
Main after TestClass: a=5 b=10 c=20 d=25

有没有办法让方法改变主程序中变量的值？谢谢!

Answer 1

您最好在 Int32 上创建自己的包装器以反射(reflect)更改，因为一旦将值分配给类的字段，它们就不再是引用，而是 Int32 的不同实例。考虑以下代码:

class Integer {
    public int Value;

    public Integer(int value) {
        Value = value;
    }

    public override string ToString() {
        return Value.ToString();
    }
}

class TestClass {
    Integer _a, _b, _c, _d;

    public TestClass(Integer a, Integer b, Integer c, Integer d) {
        _a = a;
        _b = b;
        _c = c;
        _d = d;
    }

    public void Work() {
        _a.Value = 111;
        _b.Value = 222;
        _c.Value = 333;
        _d.Value = 444;
    }
}

现在您有了一个 Integer -- Int32 的包装类。用法会给你带来结果:

Integer a = new Integer(0), b = new Integer(0), c = new Integer(0), d = new Integer(0);
Console.WriteLine("a: {0}, b: {1}, c: {2}, d: {3}", a, b, c, d);
new TestClass(a, b, c, d).Work();
Console.WriteLine("a: {0}, b: {1}, c: {2}, d: {3}", a, b, c, d);

输出是:

a: 0, b: 0, c: 0, d: 0
a: 111, b: 222, c: 333, d: 444

您可能还会发现阅读更多有关 C# 中的类和结构的信息很有用，例如http://msdn.microsoft.com/en-us/library/ms173109.aspx . (Int32 是一个结构，而在您的情况下您可能需要一个类)