为什么我应该使用var而不是类型?(复制)

Possible Duplicate:
ReSharper and var

可能重复:ReSharper和var

After I have installed ReSharper it demands(by warnings) that I use var whenever possible, for example

在安装ReSharper之后，我需要(通过警告)尽可能地使用var

UnhandledExceptionEventArgs ue = (UnhandledExceptionEventArgs) t;

ReSharper wants to turn it into

ReSharper想要把它变成

var ue = (UnhandledExceptionEventArgs) t;

I like the first version better, is there any reason to prefer var? better performance? anything? or is it just a code style?

我更喜欢第一个版本，有什么理由喜欢var吗?更好的性能吗?什么吗?还是仅仅是一种代码风格?

4 个解决方案

#1

It's really just a coding style. The compiler generates the exact same for both variants.

它只是一种编码风格。编译器为两个变体生成完全相同的结果。

See also here for the performance question:

关于性能问题，请参见这里:

Will using 'var' affect performance?
使用“var”会影响性能吗?

#2

When you say "by warnings" what exactly do you mean? I've usually seen it giving a hint that you may want to use var, but nothing as harsh as a warning.

当你说“警告”的时候，你到底是什么意思?我通常看到它给出了一个提示，提示您可能想使用var，但是没有什么比警告更严厉的了。

There's no performance difference with var - the code is compiled to the same IL. The potential benefit is in readability - if you've already made the type of the variable crystal clear on the RHS of the assignment (e.g. via a cast or a constructor call), where's the benefit of also having it on the LHS? It's a personal preference though.

没有性能差异与var - IL代码编译相同。可读性的潜在好处是——如果你已经明确的类型变量水晶RHS的任务(例如,通过一个演员或构造函数调用),也有它的好处在哪里韩吗?这是我个人的偏好。

If you don't want R# suggesting the use of var, just change the options. One thing about ReSharper: it's very configurable :)

如果您不希望r#建议使用var，只需更改选项。关于ReSharper一点:它是可配置的

#3

In this case it is just coding style.

在这种情况下，它只是编码风格。

Use of var is only necessary when dealing with anonymous types.
In other situations it's a matter of taste.

只有在处理匿名类型时才需要使用var。在其他情况下，这是一个品味问题。

#4

As the others have said, there is no difference in the compiled code (IL) when you use either of the following:

正如其他人所说的，当您使用下列任何一种代码时，编译代码(IL)没有区别:

var x1 = new object();
object x2 = new object;

I suppose Resharper warns you because it is [in my opinion] easier to read the first example than the second. Besides, what's the need to repeat the name of the type twice?

我想Resharper会警告你，因为在我看来，读第一个例子比读第二个例子更容易。此外，有什么必要重复两次类型的名称?

Consider the following and you'll get what I mean:

考虑以下内容，你就会明白我的意思:

KeyValuePair<string, KeyValuePair<string, int>> y1 = new KeyValuePair<string, KeyValuePair<string, int>>("key", new KeyValuePair<string, int>("subkey", 5));

It's way easier to read this instead:

读这篇文章要容易得多:

var y2 = new KeyValuePair<string, KeyValuePair<string, int>>("key", new KeyValuePair<string, int>("subkey", 5));

#1