马克参数在C＃/。NET为不可为空？ [英] Mark parameters as NOT nullable in C#/.NET?

问题描述

有一个简单的属性或数据的合同，我可以分配给一个函数参数起价传递在C＃/。NET p $ pvents 空？理想情况下，这也将检查在编译时间，以确保文字空不被使用的任何地方，并在运行时抛出 ArgumentNullException 。

目前我喜欢写东西......

 如果（空== ARG）
  抛出新ArgumentNullException（ARG）;
 

......为此，我希望不是每一个参数空。

在同样的注意，是有一个相对可空＆LT;＆GT; 由此，以下将失败：

 非空＆LT;字符串＆GT; S = NULL; //抛出某种异常
 

解决方案

没有什么可以在编译时，很遗憾。

我有点哈克解决方案我贴在我的博客最近，它采用了新的结构和转换。

在.NET 4.0的 code合同的东西，人生将是要好很多。这仍然是相当不错的，各地的非空性的实际语言的语法和支持，但code合约将有很大的帮助。

我也有一个扩展方法 MiscUtil 称为ThrowIfNull这使得它有点简单。

最后一点 - 任何理由使用如果（空== ARG），而不是如果（ARG == NULL）？我觉得后者更容易阅读，这个问题在C前者解决了并不适用于C＃。

Is there a simple attribute or data contract that I can assign to a function parameter that prevents null from being passed in C#/.NET? Ideally this would also check at compile time to make sure the literal null isn't being used anywhere for it and at run-time throw ArgumentNullException.

Currently I write something like ...

if (null == arg)
  throw new ArgumentNullException("arg");

... for every argument that I expect to not be null.

On the same note, is there an opposite to Nullable<> whereby the following would fail:

NonNullable<string> s = null; // throw some kind of exception

解决方案

There's nothing available at compile-time, unfortunately.

I have a bit of a hacky solution which I posted on my blog recently, which uses a new struct and conversions.

In .NET 4.0 with the Code Contracts stuff, life will be a lot nicer. It would still be quite nice to have actual language syntax and support around non-nullability, but the code contracts will help a lot.

I also have an extension method in MiscUtil called ThrowIfNull which makes it a bit simpler.

One final point - any reason for using "if (null == arg)" instead of "if (arg == null)"? I find the latter easier to read, and the problem the former solves in C doesn't apply to C#.

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