blocks|key|1319551|text|.Contains|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1319552|var+resultset+=+from+x+in+collection+where+new[]+{2,3,4,5}.Contains(x)+select+x|code-block|syntax|javascript|1319553|当然，对于你的简单问题，你可能会有这样的结果：|1319554|var+resultset+=+from+x+in+collection+where+x+>=+2+&&+x+<=+5+select+x|1319555|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|$]]

.Contains

<pre><code>var resultset = from x in collection where new[] {2,3,4,5}.Contains(x) select x
</code></pre>

Of course, with your simple problem, you could have something like:

<pre><code>var resultset = from x in collection where x &gt;= 2 &amp;&amp; x &lt;= 5 select x
</code></pre>

blocks|key|1104672|text|一条IEnumerable<T>.Contains(T)语句应该能做你想要的事情。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1104673|entityMap^0|2|Q|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

An <code>IEnumerable&lt;T&gt;.Contains(T)</code> statement should do what you're looking for.

blocks|key|1104679|text|db.SomeTable.Where(x+=>+new[]+{2,3,4,5}.Contains(x));|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1104680|或|unstyled|1104681|from+x+in+db.SomeTable
where+new[]+{2,3,4,5}.Contains(x)|1104682|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|L|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$B|C]]|$1|I|3|-4|5|F|7|N|8|@]|9|@]|A|$]]]|J|$]]

<pre><code>db.SomeTable.Where(x =&gt; new[] {2,3,4,5}.Contains(x));
</code></pre>

or

<pre><code>from x in db.SomeTable
where new[] {2,3,4,5}.Contains(x)
</code></pre>

blocks|key|1104699|text|使用IEnumerable.Contains()执行等同于SQL的操作。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1104700|var+idlist+=+new+int[]+{+2,+3,+4,+5+};

var+result+=+from+x+in+source
++++++++++where+idlist.Contains(x.Id)
++++++++++select+x;|code-block|syntax|javascript|1104701|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/bb352880.aspx^0|2|M|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

Perform the equivalent of an SQL IN with <a href="http://msdn.microsoft.com/en-us/library/bb352880.aspx" rel="noreferrer">IEnumerable.Contains()</a>.

<pre><code>var idlist = new int[] { 2, 3, 4, 5 };

var result = from x in source
 where idlist.Contains(x.Id)
 select x;
</code></pre>

blocks|key|1104726|text|使用.Contains()的一个非常基本的示例|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1104727|List<int>+list+=+new+List<int>();
for+(int+k+=+1;+k+<+10;+k%2B%2B)
{
++++list.Add(k);
}

int[]+conditionList+=+new+int[]{2,3,4};

var+a+=+(from+test+in+list
+++++++++where+conditionList.Contains(test)
+++++++++select+test);|code-block|syntax|javascript|1104728|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|$]]

A very basic example using .Contains()

<pre><code>List&lt;int&gt; list = new List&lt;int&gt;();
for (int k = 1; k &lt; 10; k++)
{
 list.Add(k);
}

int[] conditionList = new int[]{2,3,4};

var a = (from test in list
 where conditionList.Contains(test)
 select test);
</code></pre>

blocks|key|1319658|text|您可以编写help-method：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1319659|++++public+bool+Contains(int+x,+params+int[]+set)+{
++++++++return+set.Contains(x);
++++}|code-block|syntax|javascript|1319660|并使用简短的代码：|1319661|++++var+resultset+=+from+x+in+collection
++++++++++++++++++++where+Contains(x,+2,+3,+4,+5)
++++++++++++++++++++select+x;|1319662|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|$]]

You can write help-method:

<pre><code> public bool Contains(int x, params int[] set) {
 return set.Contains(x);
 }
</code></pre>

and use short code:

<pre><code> var resultset = from x in collection
 where Contains(x, 2, 3, 4, 5)
 select x;
</code></pre>

blocks|key|1319703|text|Intersect和Except更简洁一些，可能也会更快一些。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1319704|在……里面|1319705|collection.Intersect(new[]+{2,3,4,5});|code-block|syntax|javascript|1319706|不在|1319707|collection.Except(new[]+{2,3,4,5});|1319708|或|1319709|IN的方法语法|1319710|collection.Where(x+=>+new[]+{2,3,4,5}.Contains(x));|1319711|而不是IN|1319712|collection.Where(x+=>+!(new[]+{2,3,4,5}.Contains(x)));|1319713|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]]|$1|M|3|N|5|6|7|13|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|14|8|@]|9|@]|A|$]]|$1|Q|3|R|5|F|7|15|8|@]|9|@]|A|$G|H]]|$1|S|3|T|5|6|7|16|8|@]|9|@]|A|$]]|$1|U|3|V|5|F|7|17|8|@]|9|@]|A|$G|H]]|$1|W|3|-4|5|6|7|18|8|@]|9|@]|A|$]]]|X|$]]

Intersect and Except are a little more concise and will probably be a bit faster too.

IN

<pre><code>collection.Intersect(new[] {2,3,4,5});
</code></pre>

NOT IN

<pre><code>collection.Except(new[] {2,3,4,5});
</code></pre>

or

Method syntax for IN

<pre><code>collection.Where(x =&gt; new[] {2,3,4,5}.Contains(x));
</code></pre>

and NOT IN

<pre><code>collection.Where(x =&gt; !(new[] {2,3,4,5}.Contains(x)));
</code></pre>

blocks|key|1319757|text|以下是可用于搜索值列表中的值的通用扩展方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1319758|++++public+static+bool+In<T>(this+T+searchValue,+params+T[]+valuesToSearch)
++++{
++++++++if+(valuesToSearch+==+null)
++++++++++++return+false;
++++++++for+(int+i+=+0;+i+<+valuesToSearch.Length;+i%2B%2B)
++++++++++++if+(searchValue.Equals(valuesToSearch[i]))
++++++++++++++++return+true;

++++++++return+false;
++++}|code-block|syntax|javascript|1319759|这可以用作：|1319760|int+i+=+5;
i.In(45,+44,+5,+234);+//+Returns+true

string+s+=+"test";
s.In("aa",+"b",+"c");+//+Returns+false|1319761|这在条件语句中很方便。|1319762|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Following is a generic extension method that can be used to search a value within a list of values:

<pre><code> public static bool In&lt;T&gt;(this T searchValue, params T[] valuesToSearch)
 {
 if (valuesToSearch == null)
 return false;
 for (int i = 0; i &lt; valuesToSearch.Length; i++)
 if (searchValue.Equals(valuesToSearch[i]))
 return true;

 return false;
 }
</code></pre>

This can be used as:

<pre><code>int i = 5;
i.In(45, 44, 5, 234); // Returns true

string s = "test";
s.In("aa", "b", "c"); // Returns false
</code></pre>

This is handy in conditional statements.

blocks|key|1319831|text|当对原语使用Contains函数时，上述情况有效，但如果您正在处理对象(例如myListOrArrayOfObjs.Contains(efObj))呢？|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1319832|我找到了一个解决方案！将您的efObj转换为string，每个字段由_分隔(您几乎可以将其视为obj的CSV表示)|1319833|这样的示例可能如下所示：|1319834|+++++var+reqAssetsDataStringRep+=+new+List<string>();

++++++++foreach+(var+ra+in+onDemandQueueJobRequest.RequestedAssets)
++++++++{
++++++++++++reqAssetsDataStringRep.Add(ra.RequestedAssetId+%2B+"_"+%2B+ra.ImageId);
++++++++}

++++++++var+requestedAssets+=+await+(from+reqAsset+in+DbContext.RequestedAssets
+++++++++++++++++++++++++++++++++++++join+image+in+DbContext.Images+on+reqAsset.ImageId+equals+image.Id
+++++++++++++++++++++++++++++++++++++where+reqAssetsDataStringRep.Contains(reqAsset.Id+%2B+"_"+%2B+image.Id)
+++++++++++++++++++++++++++++++++++++select+reqAsset
+++++++++++++++++++++++++++++++++++++++++++).ToListAsync();|code-block|syntax|javascript|1319835|entityMap^0|6|8|12|Z|0|E|5|M|6|Y|1|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|V|8|@$9|W|A|X|B|C]|$9|Y|A|Z|B|C]|$9|10|A|11|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|12|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|13|8|@]|D|@]|E|$M|N]]|$1|O|3|-4|5|6|7|14|8|@]|D|@]|E|$]]]|P|$]]

The above situations work when the <code>Contains</code> function is used against primitives, but what if you are dealing with objects (e.g. <code>myListOrArrayOfObjs.Contains(efObj)</code>)?

I found a solution! Convert your <code>efObj</code> into a <code>string</code>, thats separated by <code>_</code> for each field (you can almost think of it as a CSV representation of your obj)

An example of such may look like this:

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

 foreach (var ra in onDemandQueueJobRequest.RequestedAssets)
 {
 reqAssetsDataStringRep.Add(ra.RequestedAssetId + "_" + ra.ImageId);
 }

 var requestedAssets = await (from reqAsset in DbContext.RequestedAssets
 join image in DbContext.Images on reqAsset.ImageId equals image.Id
 where reqAssetsDataStringRep.Contains(reqAsset.Id + "_" + image.Id)
 select reqAsset
 ).ToListAsync();
</code></pre>

With linq I have to check if a value of a row is present in an array. 
The equivalent of the sql query:

<pre><code>WHERE ID IN (2,3,4,5)
</code></pre>

How can I do it?

What is the linq equivalent to the SQL IN operator

使用linq时，我必须检查数组中是否存在行的值。相当于sql查询：WHERE ID IN (2,3,4,5)我该怎么做呢？

问与SQL IN运算符等效的linq是什么
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