IIF在C＃中相当于 [英] iif equivalent in c#
问题描述
有一个 IIF 相当于 C＃？或类似的快捷方式？
Is there a IIf equivalent in C#? Or similar shortcut?
推荐答案
C＃有？三元运算符，像其他C风格的语言。然而，这不是完全等同于IIF。有两个重要的区别。
C# has the "?" ternary operator, like other C-style languages. However, this is not perfectly equivalent to iif. There are two important differences.
要解释的第一个，这个 IIF（）调用会导致DivideByZero例外，即使前pression是真实的，因为 IIF 只是一个功能，所有的参数必须在调用之前进行评估：
To explain the first, this iif() call would cause a DivideByZero exception even though the expression is true because iif is just a function and all arguments must be evaluated before calling:
iif(true, 1, 1/0)
换句话说，IIF做的没有的短路，传统意义上的，因为你的问题表示。在另一方面，这个三元EX pression做，所以是完美的罚款：
Put another way, iif does not short circuit in the traditional sense, as your question indicates. On the other hand, this ternary expression does and so is perfectly fine:
(true)?1:1/0;
另一个区别是， IIF 不是类型安全。它接受并返回一个类型对象的参数。三元运算符使用类型推断知道什么类型的它在处理。请注意，您可以解决这个问题很容易用一个通用的实现，但开箱这就是事情是这样的。
The other difference is that iif is not type safe. It accepts and returns arguments of type object. The ternary operator uses type inference to know what type it's dealing with. Note that you can fix this very easily with a generic implementation, but out of the box that's the way it is.
如果你真的想IIF（）在C＃中，你可以把它：
If you really want iif() in C#, you can have it:
object iif(bool expression, object truePart, object falsePart)
{return expression?truePart:falsePart; }
或通用/类型安全的实现：
or a generic/type-safe implementation:
T iif<T>(bool expression, T truePart, T falsePart)
{ return expression?truePart:falsePart;}
在另一方面，如果你想三元运算符在VB，Visual Studio 2008和更高版本提供了新的如果的运算符的的作品更多如C＃的三元。它使用类型推断知道它的返回，这是运营商，而不是一个函数，所以没有讨厌的除数为零的问题。
On the other hand, if you want the ternary operator in VB, Visual Studio 2008 and later provide a new If operator that works more like C#'s ternary. It uses type inference to know what it's returning, and it's an operator rather than a function so there's no pesky divide-by-zero issues.
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