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 [英] C# - passing parameters by reference to constructor then using them from method

问题描述

在下面的代码中，我试图让类 TestClass 的方法(工作)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.

In the following code, I am trying to have a method(Work) from class TestClass change the values of some variables in the main program without having to return them. The variables are passed by reference in the TestClass constructor.

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);
    }
}

但是此代码返回:

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！

Is there any way to have the method change the values of the variables in the Main program? Thank you!

推荐答案

您最好在 Int32 上创建自己的包装器以反映更改，因为一旦将值分配给类的字段，它们将不再引用，而是 Int32 的不同实例.考虑以下代码:

You would be better off creating your own wrappers over Int32 in order for changes to be reflected, because once the values are assigned to fields of the class, they are no longer references, but rather different instances of Int32. Consider the following code:

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;
    }
}

所以现在你有一个整数——一个基于 Int32 的包装类.用法会给你带来结果:

So now you have an Integer -- a wrapper class over Int32. The usage will bring you the results:

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);

输出为:

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有关 C# 中的类和结构的更多信息很有用，例如http://msdn.microsoft.com/en-us/library/ms173109.aspx .(Int32 是一个结构体，而在您的情况下，您可能需要一个类)

You may also find it useful to read more about classes and structs in C#, e.g. http://msdn.microsoft.com/en-us/library/ms173109.aspx . (Int32 is a struct, whereas in your case you probably need a class)

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