blocks|key|4005490|text|请尝试以下操作|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4005491|var+col+=+GetTheCollection();
var+subset+=+col.Skip(250).Take(90);|code-block|syntax|javascript|4005492|或者更一般地说|4005493|public+static+IEnumerable<T>+GetRange(this+IEnumerable<T>+source,+int+start,+int+end)+{
++//+Error+checking+removed
++return+source.Skip(start).Take(end+-+start);
}|4005494|编辑+2.0解决方案|offset|length|style|BOLD|4005495|public+static+IEnumerable<T>+GetRange<T>(IEnumerable<T>+source,+int+start,+int+end+)+{
++using+(+var+e+=+source.GetEnumerator()+){+
++++var+i+=+0;
++++while+(+i+<+start+&&+e.MoveNext()+)+{+i%2B%2B;+}
++++while+(+i+<+end+&&+e.MoveNext()+)+{+
++++++yield+return+e.Current;
++++++i%2B%2B;
++++}
++}++++++
}

IEnumerable<Foo>+col+=+GetTheCollection();
IEnumerable<Foo>+range+=+GetRange(col,+250,+340);|4005496|entityMap^0|0|0|0|0|0|2|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|Y|8|@$M|Z|N|10|O|P]]|9|@]|A|$]]|$1|Q|3|R|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|S|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|T|$]]

Try the following

<pre><code>var col = GetTheCollection();
var subset = col.Skip(250).Take(90);
</code></pre>

Or more generally 

<pre><code>public static IEnumerable&lt;T&gt; GetRange(this IEnumerable&lt;T&gt; source, int start, int end) {
 // Error checking removed
 return source.Skip(start).Take(end - start);
}
</code></pre>

EDIT 2.0 Solution

<pre><code>public static IEnumerable&lt;T&gt; GetRange&lt;T&gt;(IEnumerable&lt;T&gt; source, int start, int end ) {
 using ( var e = source.GetEnumerator() ){ 
 var i = 0;
 while ( i &lt; start &amp;&amp; e.MoveNext() ) { i++; }
 while ( i &lt; end &amp;&amp; e.MoveNext() ) { 
 yield return e.Current;
 i++;
 }
 } 
}

IEnumerable&lt;Foo&gt; col = GetTheCollection();
IEnumerable&lt;Foo&gt; range = GetRange(col, 250, 340);
</code></pre>

blocks|key|4851044|text|我喜欢保持简单(如果您不一定需要枚举器)：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4851045|for+(int+i+=+249;+i+<+Math.Min(340,+list.Count);+i%2B%2B)
{
++++//+do+something+with+list[i]
}|code-block|syntax|javascript|4851046|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I like to keep it simple (if you don't necessarily need the enumerator):

<pre><code>for (int i = 249; i &lt; Math.Min(340, list.Count); i++)
{
 // do something with list[i]
}
</code></pre>

blocks|key|787031|text|将Jared的原始代码改编为.Net+2.0：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|787032|IEnumerable<T>+GetRange(IEnumerable<T>+source,+int+start,+int+end)
{
++++int+i+=+0;
++++foreach+(T+item+in+source)
++++{
++++++++i%2B%2B;
++++++++if+(i>end)+yield+break;
++++++++if+(i>start)+yield+return+item;
++++}
}|code-block|syntax|javascript|787033|并使用它：|787034|+foreach+(T+item+in+GetRange(MyCollection,+250,+340))
+{
+++++//+do+something
+}|787035|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Adapting Jared's original code for .Net 2.0:

<pre><code>IEnumerable&lt;T&gt; GetRange(IEnumerable&lt;T&gt; source, int start, int end)
{
 int i = 0;
 foreach (T item in source)
 {
 i++;
 if (i&gt;end) yield break;
 if (i&gt;start) yield return item;
 }
}
</code></pre>

And to use it:

<pre><code> foreach (T item in GetRange(MyCollection, 250, 340))
 {
 // do something
 }
</code></pre>

blocks|key|4005680|text|再次调整Jarad的代码，这个扩展方法将得到一个由项目定义的子集，而不是索引。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4005681|++++//!+Get+subset+of+collection+between+\a+start+and+\a+end,+inclusive
++++//!+Usage
++++//!+\code
++++//!+using+ExtensionMethods;
++++//!+...
++++//!+var+subset+=+MyList.GetRange(firstItem,+secondItem);
++++//!+\endcode
class+ExtensionMethods
{
++++public+static+IEnumerable<T>+GetRange<T>(this+IEnumerable<T>+source,+T+start,+T+end)
++++{
#if+DEBUG
++++++++if+(source.ToList().IndexOf(start)+>+source.ToList().IndexOf(end))
++++++++++++throw+new+ArgumentException("Start+must+be+earlier+in+the+enumerable+than+end,+or+both+must+be+the+same");
#endif
++++++++yield+return+start;

++++++++if+(start.Equals(end))
++++++++++++yield+break;++++++++++++++++++++++++++++++++++++++++++++++++++++//start+==+end,+so+we+are+finished+here

++++++++using+(var+e+=+source.GetEnumerator())
++++++++{+
++++++++++++while+(e.MoveNext()+&&+!e.Current.Equals(start));+++++++++++++++//skip+until+start++++++++++++++++
++++++++++++while+(!e.Current.Equals(end)+&&+e.MoveNext())++++++++++++++++++//return+items+between+start+and+end
++++++++++++++++yield+return+e.Current;
++++++++}
++++}
}|code-block|syntax|javascript|4005682|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Adapting Jarad's code once again, this extention method will get you a subset that is defined by item, not index.

<pre><code> //! Get subset of collection between \a start and \a end, inclusive
 //! Usage
 //! \code
 //! using ExtensionMethods;
 //! ...
 //! var subset = MyList.GetRange(firstItem, secondItem);
 //! \endcode
class ExtensionMethods
{
 public static IEnumerable&lt;T&gt; GetRange&lt;T&gt;(this IEnumerable&lt;T&gt; source, T start, T end)
 {
#if DEBUG
 if (source.ToList().IndexOf(start) &gt; source.ToList().IndexOf(end))
 throw new ArgumentException("Start must be earlier in the enumerable than end, or both must be the same");
#endif
 yield return start;

 if (start.Equals(end))
 yield break; //start == end, so we are finished here

 using (var e = source.GetEnumerator())
 { 
 while (e.MoveNext() &amp;&amp; !e.Current.Equals(start)); //skip until start 
 while (!e.Current.Equals(end) &amp;&amp; e.MoveNext()) //return items between start and end
 yield return e.Current;
 }
 }
}
</code></pre>

blocks|key|4005531|text|您也许可以使用Linq来做一些事情。我这样做的方式是将对象放入一个数组中，然后我可以根据数组id选择要处理的项。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4005532|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|$]]

You might be able to do something with Linq. The way I would do this is to put the objects into an array, then I can choose which items I want to process based on the array id.

blocks|key|1255880|text|如果您发现需要对列表和集合进行大量的切分和切分，那么学习the+C5+Generic+Collection+Library可能是值得的。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1255881|entityMap|0|LINK|mutability|MUTABLE|url|http://www.itu.dk/research/c5/^0|S|X|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

If you find that you need to do a fair amount of slicing and dicing of lists and collections, it might be worth climbing the learning curve into <a href="http://www.itu.dk/research/c5/" rel="nofollow noreferrer">the C5 Generic Collection Library</a>.

Is there a good way to enumerate through only a subset of a Collection in C#? That is, I have a collection of a large number of objects (say, 1000), but I'd like to enumerate through only elements 250 - 340. Is there a good way to get an Enumerator for a subset of the collection, without using another Collection?

Edit: should have mentioned that this is using .NET Framework 2.0.

Enumerate through a subset of a Collection 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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有没有一种很好的方法来在C#中只枚举集合的一个子集？也就是说，我有一个包含大量对象(比如1000个)的集合，但我只想枚举250 - 340个元素。有没有一种好的方法来获得集合的子集的枚举数，而不使用另一个集合？编辑:应该提到它使用的是.NET Framework2.0。

问在C#中枚举集合的子集吗？
EN

回答 6

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问在C#中枚举集合的子集吗？EN

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问在C#中枚举集合的子集吗？
EN