blocks|key|2759755|text|哪个更快？
|type|blockquote|depth|inlineStyleRanges|entityRanges|data|2759756|unstyled|2759757|两者都是一样的。|2759758|是否依赖于这种类型？
|2759759|2759760|我不知道您在这里问的是什么，但是这些代码片段一旦编译，它们之间就没有什么区别了，所以我将使用no。|2759761|在这两种情况下都分配了多少内存，以及何时分配了内存？
|2759762|2759763|他们都是一样的。对于int示例，对于所有情况，它都是32位。对于List示例，这三个都将为引用分配一个单词，以及实际列表实例的内存。|offset|length|style|CODE|2759764|entityMap^0|0|0|0|0|0|0|0|0|A|3|W|4|0^^$0|@$1|2|3|4|5|6|7|V|8|@]|9|@]|A|$]]|$1|B|3|-4|5|C|7|W|8|@]|9|@]|A|$]]|$1|D|3|E|5|C|7|X|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|Y|8|@]|9|@]|A|$]]|$1|H|3|-4|5|C|7|Z|8|@]|9|@]|A|$]]|$1|I|3|J|5|C|7|10|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|11|8|@]|9|@]|A|$]]|$1|M|3|-4|5|C|7|12|8|@]|9|@]|A|$]]|$1|N|3|O|5|C|7|13|8|@$P|14|Q|15|R|S]|$P|16|Q|17|R|S]]|9|@]|A|$]]|$1|T|3|-4|5|C|7|18|8|@]|9|@]|A|$]]]|U|$]]

<blockquote>
 Which faster?
</blockquote>

Neither, they're the same.

<blockquote>
 There is a dependence on the type?
</blockquote>

I'm not sure what you're asking here, but there's no difference between any of those code snippets once they are compiled, so I'll go with no.

<blockquote>
 How much memory is allocated in both situation and when that memory allocated?
</blockquote>

It's the same for all of them. For the <code>int</code> example it's 32 bits for all cases. For the <code>List</code> example all three will allocate one word for the reference, plus the memory for the actual list instance.

blocks|key|2560964|text|这是纯粹的编译步骤特性。编译器推断左侧表达式的类型，并将其用作变量类型。因此产生的IL将是相同的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2560965|所以：|2560966|var+list1+=+new+List<int>();
List<int>+list2+=+new+List<int>();|code-block|syntax|javascript|2560967|完全相同。但是，我可以看到一些例子，其中指定类型可能会产生一些效果，例如：|2560968|var+i1+=+5;
int+i2+=+5;
//vs:
var+i2+=+5;
object+i2+=+5;|2560969|因此，如果实际表达式类型与声明变量类型完全相同，那么它们是完全相同的。但是，如果表达式类型和变量类型不相同，var可能是不同的。|offset|length|style|CODE|2560970|entityMap^0|0|0|0|0|0|1I|3|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|X|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|Y|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|Z|8|@$O|10|P|11|Q|R]]|9|@]|A|$]]|$1|S|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|T|$]]

It is purely compilation step feature. Compiler infers the type of the expression on the left, and uses it as variable type. So resulting IL will be the same.

So:

<pre><code>var list1 = new List&lt;int&gt;();
List&lt;int&gt; list2 = new List&lt;int&gt;();
</code></pre>

Are completely identical. But I can see some examples where specifying type can have some effects, like:

<pre><code>var i1 = 5;
int i2 = 5;
//vs:
var i2 = 5;
object i2 = 5;
</code></pre>

So if actual expression type is exactly the same as declared variable type then they are completely identical. But <code>var</code> can be different if expression type and variable types are not the same.

blocks|key|2759788|text|var关键字只是一个语法糖。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2759789|它不存在于IL中，所以没有区别。|2759790|重复主题：|2759791|Is+there+a+performance+hit+in+using+the+'var'+keyword+in+C#?|2759792|Will+using+'var'+affect+performance?|2759793|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/1756392/is-there-a-performance-hit-in-using-the-var-keyword-in-c|1|https://stackoverflow.com/questions/356846/c-sharp-var-vs-specific-type-performance^0|0|3|0|0|0|0|1O|0|0|0|10|1|0^^$0|@$1|2|3|4|5|6|7|X|8|@$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|10|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|11|8|@]|D|@]|E|$]]|$1|J|3|K|5|6|7|12|8|@]|D|@$9|13|A|14|1|15]]|E|$]]|$1|L|3|M|5|6|7|16|8|@]|D|@$9|17|A|18|1|19]]|E|$]]|$1|N|3|-4|5|6|7|1A|8|@]|D|@]|E|$]]]|O|$P|$5|Q|R|S|E|$T|U]]|V|$5|Q|R|S|E|$T|W]]]]

<code>var</code> keyword is just a syntactical sugar. 

It is not present in the IL, so there's no difference.

Duplicate topics:

<a href="https://stackoverflow.com/questions/1756392/is-there-a-performance-hit-in-using-the-var-keyword-in-c">Is there a performance hit in using the &#39;var&#39; keyword in C#?</a>

<a href="https://stackoverflow.com/questions/356846/c-sharp-var-vs-specific-type-performance">Will using &#39;var&#39; affect performance?</a>

blocks|key|2759825|text|何时使用var，何处不使用。(因为这里已经回答了所有其他问题)为什么是var?？-匿名类型和LINQ|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2759826|匿名(临时使用)类型：|2759827|var+v+=+new+{+Amount+=+108,+Message+=+"Hello"+};|code-block|syntax|javascript|2759828|常规：|2759829|使用：|2759830|var+myList+=+new+List<string>();|2759831|在这里，很明显，myList有什么类型的代码读取是好的。|2759832|不要使用：|2759833|var+properties+=+myPropertyHandler.GetProperties();|2759834|在这里，您不知道GetProperties返回的类型-代码读取是不好的。声明：|2759835|AppProperties+properties+=++myPropertyHandler.GetProperties();|2759836|entityMap^0|4|3|Z|3|0|0|0|0|0|0|8|6|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|14|8|@$9|15|A|16|B|C]|$9|17|A|18|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|19|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|1A|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|1B|8|@]|D|@]|E|$]]|$1|O|3|P|5|6|7|1C|8|@]|D|@]|E|$]]|$1|Q|3|R|5|J|7|1D|8|@]|D|@]|E|$K|L]]|$1|S|3|T|5|6|7|1E|8|@$9|1F|A|1G|B|C]]|D|@]|E|$]]|$1|U|3|V|5|6|7|1H|8|@]|D|@]|E|$]]|$1|W|3|X|5|J|7|1I|8|@]|D|@]|E|$K|L]]|$1|Y|3|Z|5|6|7|1J|8|@]|D|@]|E|$]]|$1|10|3|11|5|J|7|1K|8|@]|D|@]|E|$K|L]]|$1|12|3|-4|5|6|7|1L|8|@]|D|@]|E|$]]]|13|$]]

When to use <code>var</code> and where not to use. (Because all other questions are answered here already)
Why <code>var</code>?? - Anonymous types and LINQ

Anonymous (temporary use) types:

<pre><code>var v = new { Amount = 108, Message = "Hello" };
</code></pre>

General:

Use:

<pre><code>var myList = new List&lt;string&gt;();
</code></pre>

Here it is obvious what type <code>myList</code> has - code reading is good

Don't use:

<pre><code>var properties = myPropertyHandler.GetProperties();
</code></pre>

Here you have no idea what type returned by GetProperties - code reading is bad. Declare:

<pre><code>AppProperties properties = myPropertyHandler.GetProperties();
</code></pre>

blocks|key|2561041|text|Var关键字只有在C#编译器生成程序集的IL代码时才有效，要创建的变量类型由表达式的右侧计算(必须指定，不能为null)。Var不影响运行时中的任何内容。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2561042|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Var keyword works only then C# compiler generates assembly's IL code, the type of variable to create is calculated by the right side of expression (which must be specified and cannot be null). Var does not affects anything in runtime.

blocks|key|1737630|text|var是从右边语句返回的任何内容中推断出来的。这是由编译器完成的，所以当程序实际运行时，没有区别。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1737631|但是，请注意，如果语句生成意外类型，则不会得到编译器错误。|1737632|entityMap^0|0|3|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|M|8|@]|D|@]|E|$]]|$1|H|3|-4|5|6|7|N|8|@]|D|@]|E|$]]]|I|$]]

<code>var</code> is inferred from whatever is returned from the statement on the right. This is done by the compiler, so when the program is actually run, there is no difference.

Watch out, however, that you will not get a compiler error if the statement produces an unintended type.

I really confused about usage <code>var</code> keyword in <code>C#</code>. I know, that <code>var</code> make code more easier to read, but what about speed and memory?

A.

<ol>
<li><code>var a = 100;</code> </li>
<li><code>int b = 100;</code></li>
<li><code>int c; c = 100;</code></li>
</ol>

B.

<ol>
<li><code>var listA = new List&lt;obj&gt;();</code></li>
<li><code>List&lt;obj&gt;listB = new List&lt;obj&gt;();</code></li>
<li><code>List&lt;obj&gt;listC; listC = new List&lt;obj&gt;();</code></li>
</ol>

Which faster? 
There is a dependence on the type? 
How much memory is allocated in both situation and when that memory allocated?

Usage of the C# var keyword

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我真的对在var中使用C#关键字感到困惑。我知道，var使代码更容易阅读，但是速度和内存又如何呢？一个。var a = 100;int b = 100;int c; c = 100;B.var listA = new List<obj>();List<obj>listB = new List<obj>();List<obj>listC; listC = new List<obj>();哪个更快？是

问C# var关键字的使用
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