是只读的自动实现的属性可能吗？ [英] Is read-only auto-implemented property possible?

问题描述

我发现一个话题MSDN 的那个会谈，是的，这是可能的。

I found a topic on MSDN that talks that yes, this is possible.

我做了一个测试，这似乎打破了这个说法：

I did a test that seems to break this statement:

using System;

namespace Test
{
    class Program
    {
        static void Main(string[] args)
        {
            Foo f = new Foo("1");
            Console.WriteLine(f.Bar); // prints 1
            f.Test("2");
            Console.WriteLine(f.Bar);// successfully prints 2
        }
    }

    class Foo
    {
        public Foo(string b)
        {
            this.Bar = b;
        }

        public string Bar { get; private set; }

        public void Test(string b)
        {
            // this would be impossible for readonly field!
            // next error would be occur: CS0191 or CS0191
            // A readonly field cannot be assigned to (except in a constructor or a variable initializer)
            this.Bar = b; 
        }
    }
}

我在哪里错了？

Where am I wrong?

推荐答案

下面写早在2010年在C＃6的答案（被释放，2015年），你的可以的写只读自动-implemented属性：

The answer below was written back in 2010. In C# 6 (to be released in 2015) you can write read-only automatically-implemented properties:

// This can only be assigned to in a constructor
public int Foo { get; }

---

您说的没错。正确的只读自动实现的属性，目前是不可能的。使得二传手私人是不一样的东西，不管什么一些书籍和MSDN可能会说的：）

---

You're absolutely right. Properly read-only automatically implemented properties are currently impossible. Making the setter private isn't the same thing, regardless of what some books and MSDN might say :)

如果我统治的时代，这将不会是这样。当我看到一些语言的设计者在 NDC 2010 六月（请走吧！）我打算劝说，贿赂，哄着，一般使我自己滋扰，直到他们同意。这只是一个极薄的功能，毕竟。

If I ruled the world, this would not be the case. When I see some of the language designers at NDC 2010 in June (please come along!) I intend to try to persuade, bribe, cajole and generally make a nuisance of myself until they agree. It's just one wafer-thin feature, after all.

望着那MSDN文章，文字本身不说，它创建了一个只读的自动性。它创建了一个不可变的类型的使用的自动属性，这是正确的。唯一的问题位是说评论

Looking at that MSDN article, the text itself doesn't say that it creates a read-only automatic property. It creates an immutable type using an automatic property, and that's correct. The only problematic bits are the comments saying

// Read-only properties.

...这是绝对错误的。该框架同意我们：

... which are definitely wrong. The framework agrees with us:

var prop = typeof(Contact).GetProperty("Name");
Console.WriteLine(prop.CanWrite); // Prints True

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