是否有必要使用构造函数注入检查空值？ [英] Is it necessary to check null values with constructor injection?

问题描述

我正在使用.NET Core构造函数注入。
在一位同事的代码审查中，他提出了一个问题，即我是否应该检查控制器中注入的依赖项的空值。

I'm using .NET Core constructor injection. In a code review from a colleague, he raised the question if I should check for null values on injected dependencies in controllers.

由于该框架负责创建服务的实例，在我看来，它将处理所有错误，并且永远不会将空值依赖项传递给构造函数。但是我没有任何事实证据，因此我想知道是否有必要进行空检查。

Since the framework is responsible for creating an instance of the service, it seems to me that it would take care of any errors and never have a null value dependency passed to a constructor. I don't have any factual evidence for this though, so I'd like to know if it's possible that a null check may be necessary.

例如，我是否应该检查以下代码中的 myService是否为空？ （假设代码配置为使用DI）

For example, should I check if 'myService' is null in the following code? (Assuming the code is configured to use DI)

public class MyController
{
    private readonly IMyService _myService;

    public MyController(IMyService myService) 
    {
        _myService = myService;
    }
}

推荐答案

是否需要使用构造函数注入检查空值？

Is it necessary to check null values with constructor injection?

这取决于。

• 您和（可能）某些队友在（很幸运）代码审查环境中使用的此内部代码吗？

不要。这不是必需的。该框架不允许这样做。

Don't. It's not necessary. The framework doesn't allow this.

• 此代码是公共库中的，供多人使用还是在依赖注入之后没有实际使用？ / li>
  

• Is this code in a public library, used by multiple people or not actually following Dependency Injection?

然后执行此操作。手动实例化会在某个地方导致NullReferenceException，并且很难找到它们。

Then do it. A manual instantation would result in a NullReferenceException somewhere and those are hard to track down.

也就是说，使用类似这样的东西：

That said, using something like this:

public MyController(IMyService myService) 
{
    if (myService == null)
    {
        throw new ArgumentNullException(nameof(myService));
    }

    _myService = myService;
}

这是一张非常便宜的支票，如果有人通过 null 由于某些原因。

Is an extremely cheap check and it's much easier to track down if someone passes null for some reason.

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