我怎么能证明一个方法永远不会在C＃（契约式设计）返回null [英] How can I show that a method will never return null (Design by contract) in C#

问题描述

我有一个永远不会返回空对象的方法。我想讲清楚，使我的API的用户不必写这样的代码：

I have a method which never returns a null object. I want to make it clear so that users of my API don't have to write code like this:

if(Getxyz() != null)
{
  // do stuff
}

我怎样才能显示这个意图是什么？

How can I show this intent?

推荐答案

Unforutnately没有办法内置到C＃

Unforutnately there is no way built in to C#

您可以记录这个事实，但这将不会被自动检查。

You can document this fact, but this won't be automatically checked.

如果您使用的是ReSharper的，那么就可以设置检查这个当正确方法标有[NOTNULL]属性。

If you are using resharper, then it can be set up to check this properly when the method is marked with a [NotNull] attribute.

否则，您可以使用的微软合同库并添加类似于以下到你的方法什么的，但是这是这样一个简单的注解了不少额外的冗词。

Otherwise you can use the Microsoft Contracts library and add something similar to the following to your method, but this is quite a lot of extra verbiage for such a simple annotation.

Contract.Ensures(Contract.Result<string>() != null)

规格＃通过允许解决了这个问题！该类型之后将其标记为一个非空类型，例如：

Spec# solved this problem by allowing a ! after the type to mark it as a non-null type, eg

string! foo

但规格＃只能用于靶向.NET2，并由代码契约已经篡库。

but Spec# can only be used to target .NET2, and has been usurped by the Code Contracts library.

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