C# 结构 "this = ...."

Question

我刚刚在反射器中浏览了一个文件，并在结构构造函数中看到了这个:

this = new Binder.SyntaxNodeOrToken();

我以前从未见过该术语。有人能解释一下这个赋值在 C# 中的含义吗？谷歌很难。

Answer 1

它基本上取代了值(value)。它有效地将所有字段从右侧复制到左侧......除了即使字段是只读的，它也能工作。是的，它确实看起来很奇怪，而且有点吓人。

例子:

using System;

class Test
{
    static void Main()
    {
        Point point = new Point(10, 20);
        point.ReplaceWith(new Point(2, 3));
        Console.WriteLine(point); // (2, 3)
    }
}

struct Point
{
    private readonly int x;
    private readonly int y;

    public Point(int x, int y)
    {
        this.x = x;
        this.y = y;
    }

    public void ReplaceWith(Point other)
    {
        this = other;
    }

    public override string ToString()
    {
        return string.Format("({0}, {1})", x, y);
    }
}

有关详细信息，请阅读 C# 4 规范的第 7.6.7 节，其中包括:

• [text about its use in a struct constructor]

• When this is used in a primary-expression within an instance method or instance accessor of a struct, it is classified as a variable. The type of the variable is the instance type of the struct within which the usage occurs.

  • If the method or accessor is not an iterator, the this variable represents the struct for which the method or accessor was invoked, and behaves exactly the same as a ref parameter of the struct type.

  • [text about iterators]