blocks|key|1499488|text|我试着给你们举个例子|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1499489|下面是一种典型的操作方法，它填充列表对象，然后返回它：|1499490|private+IEnumerable<int>+GetNumbers()
{
++++var+list+=+new+List<int>();
++++for+(var+i+=+0;+i+<+10;+i%2B%2B)
++++{
++++++++list.Add(i);
++++}
++++return+list;
}|code-block|syntax|javascript|1499491|like关键字依次返回如下项：|1499492|private+IEnumerable<int>+GetNumbers()
{
++++for+(var+i+=+0;+i+<+10;+i%2B%2B)
++++{
++++++++yield+return+i;
++++}
}|1499493|因此，假设调用GetNumbers函数的代码如下所示：|1499494|foreach+(int+number+in+GetNumbers())
{
+++if+(number+==+5)
+++{
+++++++//do+something+special...
+++++++break;
+++}
}|1499495|如果不使用收益率，则必须从0-10生成整个列表，然后返回，然后迭代，直到找到数字5。|1499496|现在，由于产生关键字，您将只生成数字，直到您到达您要寻找的，并打破循环。|1499497|我不知道我是否足够清楚..。|1499498|entityMap^0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Z|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|10|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|11|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|12|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|13|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|14|8|@]|9|@]|A|$G|H]]|$1|Q|3|R|5|6|7|15|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|16|8|@]|9|@]|A|$]]|$1|U|3|V|5|6|7|17|8|@]|9|@]|A|$]]|$1|W|3|-4|5|6|7|18|8|@]|9|@]|A|$]]]|X|$]]

I'm going to try and give you an example

Here's the classical way of doing, which fill up a list object and then returns it:

<pre><code>private IEnumerable&lt;int&gt; GetNumbers()
{
 var list = new List&lt;int&gt;();
 for (var i = 0; i &lt; 10; i++)
 {
 list.Add(i);
 }
 return list;
}
</code></pre>

the yield keyword returns items one by one like this :

<pre><code>private IEnumerable&lt;int&gt; GetNumbers()
{
 for (var i = 0; i &lt; 10; i++)
 {
 yield return i;
 }
}
</code></pre>

so imagine the code that calls the GetNumbers function as following:

<pre><code>foreach (int number in GetNumbers())
{
 if (number == 5)
 {
 //do something special...
 break;
 }
}
</code></pre>

without using yield you would have to generate the whole list from 0-10 which is then returned, then iterated over until you find the number 5.

Now thanks to the yield keyword, you will only generate numbers until you reach the one you're looking for and break out the loop.

I don't know if I was clear enough..

blocks|key|739485|text|我的问题是，我什么时候使用它？有什么例子吗?我没有别的选择，只能用产量？为什么有人觉得C#需要另一个关键字？|type|blockquote|depth|inlineStyleRanges|entityRanges|data|739486|您所链接的这篇文章提供了一个很好的示例，说明了何时以及如何使用它。|unstyled|739487|我也不想引用你自己链接的一篇文章，但万一它太长了，你也没看过。|739488|生成关键字向编译器发出信号，表示它出现的方法是迭代器块。编译器生成一个类来实现迭代器块中表示的行为。|offset|length|style|BOLD|739489|public+static+System.Collections.IEnumerable+Power(int+number,+int+exponent)
{
++++int+counter+=+0;
++++int+result+=+1;
++++while+(counter%2B%2B+<+exponent)
++++{
++++++++result+=+result+*+number;
++++++++yield+return+result;
++++}
}|code-block|syntax|javascript|739490|在上面的示例中，收益率语句在迭代器块中使用。调用Power方法时，它返回一个可枚举对象，该对象包含一个数字的幂。注意，Power方法的返回类型是System.Collections.IEnumerable+(迭代器接口类型)。|739491|因此，编译器根据方法执行过程中产生的内容自动生成一个IEnumerable接口。|739492|为了完整起见，下面是一个简化的示例：|739493|public+static+System.Collections.IEnumerable+CountToTen()
{
++++int+counter+=+0;
++++while+(counter%2B%2B+<+10)
++++{
++++++++yield+return+counter;
++++}
}

public+static+Main(string[]...)
{
++++foreach(var+i+in+CountToTen())
++++{
++++++++Console.WriteLine(i);
++++}
}|739494|entityMap^0|0|0|0|N|5|0|0|E|4|0|0|0|0^^$0|@$1|2|3|4|5|6|7|11|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|12|8|@]|9|@]|A|$]]|$1|E|3|F|5|D|7|13|8|@]|9|@]|A|$]]|$1|G|3|H|5|D|7|14|8|@$I|15|J|16|K|L]]|9|@]|A|$]]|$1|M|3|N|5|O|7|17|8|@]|9|@]|A|$P|Q]]|$1|R|3|S|5|D|7|18|8|@$I|19|J|1A|K|L]]|9|@]|A|$]]|$1|T|3|U|5|D|7|1B|8|@]|9|@]|A|$]]|$1|V|3|W|5|D|7|1C|8|@]|9|@]|A|$]]|$1|X|3|Y|5|O|7|1D|8|@]|9|@]|A|$P|Q]]|$1|Z|3|-4|5|D|7|1E|8|@]|9|@]|A|$]]]|10|$]]

<blockquote>
 my question is, when do I use it? Is there any example out there where I have there is no other choice but using yield? Why did someone feel C# needed another keyword?
</blockquote>

The article you linked provided a nice example of when and how it is used.

I hate to quote an article you yourself linked too, but incase it's too long, and you didn't read it.

The yield keyword signals to the compiler that the method in which it appears is an iterator block. The compiler generates a class to implement the behavior that is expressed in the iterator block.

<pre><code>public static System.Collections.IEnumerable Power(int number, int exponent)
{
 int counter = 0;
 int result = 1;
 while (counter++ &lt; exponent)
 {
 result = result * number;
 yield return result;
 }
}
</code></pre>

In the above example, the yield statement is used inside an iterator block. When the Power method is invoked, it returns an enumerable object that contains the powers of a number. Notice that the return type of the Power method is System.Collections.IEnumerable, an iterator interface type.

So the compiler automatically generates a IEnumerable interfaced based on the things that were yielded during the method's execution.

Here is a simplified example, for the sake of completeness:

<pre><code>public static System.Collections.IEnumerable CountToTen()
{
 int counter = 0;
 while (counter++ &lt; 10)
 {
 yield return counter;
 }
}

public static Main(string[]...)
{
 foreach(var i in CountToTen())
 {
 Console.WriteLine(i);
 }
}
</code></pre>

<blockquote>
 Possible Duplicate: 
 <a href="https://stackoverflow.com/questions/410026/proper-use-of-yield-return">Proper Use of yield return</a> 
</blockquote>



What is the use of the <code>yield</code> keyword in C#?

I didn't understand it from <a href="http://msdn.microsoft.com/en-us/library/9k7k7cf0.aspx" rel="nofollow noreferrer">the MSDN reference</a>... can someone explain it to me please?

What is the use of the "yield" keyword in C#?

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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可能重复：yield关键字在C#中的用途是什么？我不明白的意思.有人能给我解释一下吗？

问在C#中“产生”关键字的用途是什么？
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