问题描述

我想确保永远不会从代码中显式调用方法(在我的情况下实际上是构造函数).它只能在运行时通过反射调用.为此，我想在方法上应用一个属性，如果调用该方法会产生编译器错误，例如:

I would like to ensure that a method (actually a constructor in my case) is never called explicitly from code. It should only be called through reflection at runtime. To do that, I would like to apply an attribute on the method that would generate a compiler error if the method is called, something like :

[NotCallable("This method mustn't be called from code")]
public void MyMethod()
{
}

我知道我可以将方法设为私有，但在这种情况下，我将无法通过部分信任上下文中的反射来调用它...

I know that I could make the method private, but in that case I wouldn't be able to call it through reflection in a partial trust context...

为了完整起见，这里有更多关于我为什么需要这样做的详细信息:

For completeness, here's more details about why I need to do that :

我正在实现一个可重用的 Singleton<T> 类，基于 Jon Skeet 的文章.到目前为止，这是我的代码:

I'm implementing a reusable Singleton<T> class, based on Jon Skeet's article. Here's my code so far :

public static class Singleton<T>
{
    public static T Instance
    {
        get
        {
            return LazyInitializer._instance;
        }
    }

    private class LazyInitializer
    {
        // Explicit static constructor to tell C# compiler
        // not to mark type as beforefieldinit
        static LazyInitializer()
        {
            Debug.WriteLine(string.Format("Initializing singleton instance of type '{0}'", typeof(T).FullName));
        }

        internal static readonly T _instance = (T)Activator.CreateInstance(typeof(T), true);
    }
}

(注意我使用 Activator.CreateInstance 创建 T 实例的方式)

(Note the way I create the T instance using Activator.CreateInstance)

然后我可以将它与这样的类一起使用:

I can then use it with a class like that :

private class Foo
{
    protected Foo()
    {
    }

    public string Bar { get; private set; }
}

并调用Singleton<Foo>.Instance来访问实例.

在部分信任的情况下，它不会工作，因为 Foo 构造函数不是公共的.但是如果我把它公开，没有什么能阻止从代码中显式调用它......我知道我可以在 Foo 构造函数上应用 ObsoleteAttribute ，但它只会生成一个警告，许多人只是忽略警告.

In partial trust, it won't work because the Foo constructor is not public. But if I make it public, nothing will prevent calling it explicitly from code... I know I could apply the ObsoleteAttribute on the Foo constructor, but it will only generate a warning, and many people just ignore warnings.

那么，是否有类似于 ObsoleteAttribute 的属性会生成错误而不是警告?

So, is there an attribute similar to ObsoleteAttribute that would generate an error instead of a warning ?

任何建议将不胜感激

推荐答案

您可以使用 ObsoleteAttribute 构造函数，它接受一个布尔值，您可以使用它指示调用该方法是一个编译错误:

You can use the ObsoleteAttribute constructor that takes a boolean with which you can indicate that calling the method is a compilation error:

[Obsolete("Don't use this", true)]

但是，如果我是你，我会重新考虑我的设计，因为这样做并不是 API 设计良好的标志.

However, if I were you, I'd reconsider my design, as doing this isn't a sign of a well-designed API.

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