哪个性能更好？和安道尔一样 [英] Which is better for performance? And vs AndAlso

问题描述

在编写If语句时，我总是在需要时使用和，如：

When writing an If statement, I've always used And when needed like:

If 1=1 And 2=2 Then

我唯一使用过的时间 AndAlso 如果第二个条件会出错，如果第一个条件不是这样的话：

The only time I ever used AndAlso is if the second condition will error if the first isnt true like:

If Not IsDbNull(Value) AndAlso Value=2 Then

然而，最近我听说过 AndAlso 的性能优于和，因为只有当第一个条件为真时才会读取第二个条件。

However, recently I've heard that AndAlso is better for performance than And as the second condition is only read when the first is true.

在这种情况下，我应该只使用 AndAlso ？

In this case, should I always just use AndAlso?

推荐答案

是的， AndAlso 可以快于和，因为它不会如果先前的条件证明是错误的，则评估后续条件。

Yes, AndAlso can be faster than And, because it doesn't evaluate subsequent conditions if an earlier condition proves false.

和是对早期版本的Visual Basic的回归。 br>
大多数（我毫不犹豫地说）所有现代语言都使用布尔运算符那些不严格需要评估的短路情况。

And is a throwback to earlier versions of Visual Basic.
Most (I hesitate to say all) modern languages use boolean operators that short-circuit conditions that don't strictly need to be evaluated.

例如。 && C风格语言的和运算符都表现为 AndAlso 。

e.g. && the and operator for C style languages all perform as AndAlso.

如果你有很多使用和和或的代码，请注意全球如果第二个条件涉及具有副作用的函数调用，则搜索和替换可以更改现有行为。

Be careful if you've lots of code that use And and Or, a global search and replace can change existing behaviour, if the second condition involves a function call that has side effects.

我更喜欢使用 AndAlso 和 OrElse 除非您特别要求和&提供的功能。 或

I would prefer using AndAlso and OrElse unless you specifically require the functionality provided by And & Or

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