如何比较可空类型？ [英] How to compare nullable types?

问题描述

我有几个地方我需要比较2（可为空）值，看看它们是相同的。

I have a few places where I need to compare 2 (nullable) values, to see if they're the same.

我觉得应该有东西在该框架支持这一点，但无法找到任何东西，这样反而有以下几点：

I think there should be something in the framework to support this, but can't find anything, so instead have the following:

public static bool IsDifferentTo(this bool? x, bool? y)
{
    return (x.HasValue != y.HasValue) ? true : x.HasValue && x.Value != y.Value;
}

然后，在代码中，我有如果（X。 IsDifferentTo（Y））...

然后我有可能为空的整数，可为空双打等类似的方法。

I then have similar methods for nullable ints, nullable doubles etc.

有没有一个更简单的方法来查看两个可空类型是相同的。

Is there not an easier way to see if two nullable types are the same?

更新：

事实证明，这种方法存在的原因是因为代码已经从VB.Net，这里没有=无返回false转换（对比C＃其中null == NULL返回true ）。在VB.Net代码应该用 .Equals ... 代替。

Turns out that the reason this method existed was because the code has been converted from VB.Net, where Nothing = Nothing returns false (compare to C# where null == null returns true). The VB.Net code should have used .Equals... instead.

推荐答案

C＃支持解禁的运营商，因此，如果类型（布尔在这种情况下？）在编译时知道你应该只能够使用：

C# supports "lifted" operators, so if the type (bool? in this case) is known at compile you should just be able to use:

return x != y;

如果你需要仿制药，那么 EqualityComparer< T> .DEFAULT 是你的朋友！

If you need generics, then EqualityComparer<T>.Default is your friend:

return !EqualityComparer<T>.Default.Equals(x,y);

请注意，但是，这两种方法都使用空==空的方法（对比ANSI SQL）。如果你需要！空= NULL ，那么你就必须测试分别：

Note, however, that both of these approaches use the "null == null" approach (contrast to ANSI SQL). If you need "null != null" then you'll have to test that separately:

return x == null || x != y;

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