blocks|key|1555598|text|尝试使用两个单独的步骤：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1555599|//+create+a+Dictionary+/+Set+/+Collection+fids+first
var+fids+=+(from+fb+in+FooBar
++++++++++++where+fb.BarID+=+1000
++++++++++++select+new+{+fooID+=+fb.FooID,+barID+=+fb.BarID+})
++++++++++++.ToDictionary(x+=>+x.fooID,+x+=>+x.barID);

from+f+in+Foo
where+fids.HasKey(f.FooId)
select+f|code-block|syntax|javascript|1555600|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|$]]

<p>Try using two separate steps:</p>

<pre><code>// create a Dictionary / Set / Collection fids first
var fids = (from fb in FooBar
            where fb.BarID = 1000
            select new { fooID = fb.FooID, barID = fb.BarID })
            .ToDictionary(x =&gt; x.fooID, x =&gt; x.barID);

from f in Foo
where fids.HasKey(f.FooId)
select f
</code></pre>


blocks|key|1555609|text|from+f+in+Foo
++++where+f.FooID+==
++++++++(
++++++++++++FROM+fb+in+FooBar
++++++++++++WHERE+fb.BarID+==+1000
++++++++++++select+fb.FooID

++++++++)
++++select+f;|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1555610|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>from f in Foo
    where f.FooID ==
        (
            FROM fb in FooBar
            WHERE fb.BarID == 1000
            select fb.FooID

        )
    select f;
</code></pre>


blocks|key|1770674|text|尝尝这个|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1770675|var+fooids+=+from+fb+in+foobar+where+fb.BarId=1000+select+fb.fooID
var+ff+=+from+f+in+foo+where+f.FooID+=+fooids+select+f|code-block|syntax|javascript|1770676|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|$]]

<p>Try this</p>

<pre><code>var fooids = from fb in foobar where fb.BarId=1000 select fb.fooID
var ff = from f in foo where f.FooID = fooids select f
</code></pre>


blocks|key|1770730|text|看看this+article吧。基本上，如果您想获得IN的等价物，则需要首先构造一个内部查询，然后使用Contains()方法。以下是我的翻译尝试：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1770731|var+innerQuery+=+from+fb+in+FoorBar+where+fb.BarId+=+1000+select+fb.FooId;
var+result+=+from+f+in+Foo+where+innerQuery.Contains(f.FooId)+select+f;|code-block|syntax|javascript|1770732|entityMap|0|LINK|mutability|MUTABLE|url|http://blog.wekeroad.com/2008/02/27/creating-in-queries-with-linq-to-sql^0|2|C|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]]]]

<p>Have a look at <a href="http://blog.wekeroad.com/2008/02/27/creating-in-queries-with-linq-to-sql" rel="noreferrer">this article</a>. Basically, if you want to get the equivalent of IN, you need to construct an inner query first, and then use the Contains() method. Here's my attempt at translating:</p>

<pre><code>var innerQuery = from fb in FoorBar where fb.BarId = 1000 select fb.FooId;
var result = from f in Foo where innerQuery.Contains(f.FooId) select f;</code></pre>


blocks|key|1770759|text|在LINQ+to+SQL中实现IN的一般方法|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1770760|var+q+=+from+t1+in+table1
++++++++let+t2s+=+from+t2+in+table2
++++++++++++++++++where+<Conditions+for+table2>
++++++++++++++++++select+t2.KeyField
++++++++where+t2s.Contains(t1.KeyField)
++++++++select+t1;|code-block|syntax|javascript|1770761|在LINQ+to+SQL中实现EXISTS的一般方法|1770762|var+q+=+from+t1+in+table1
++++++++let+t2s+=+from+t2+in+table2
++++++++++++++++++where+<Conditions+for+table2>
++++++++++++++++++select+t2.KeyField
++++++++where+t2s.Any(t1.KeyField)
++++++++select+t1;|1770763|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|$]]

<h1>General way to implement IN in LINQ to SQL</h1>

<pre><code>var q = from t1 in table1
        let t2s = from t2 in table2
                  where &lt;Conditions for table2&gt;
                  select t2.KeyField
        where t2s.Contains(t1.KeyField)
        select t1;
</code></pre>

<h1>General way to implement EXISTS in LINQ to SQL</h1>

<pre><code>var q = from t1 in table1
        let t2s = from t2 in table2
                  where &lt;Conditions for table2&gt;
                  select t2.KeyField
        where t2s.Any(t1.KeyField)
        select t1;
</code></pre>


blocks|key|1770773|text|var+foos+=+Foo.Where<br>
(+f+=>+FooBar.Where(fb.BarId+==+1000).Select(fb+=>+fb.FooId).Contains(f.FooId));|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1770774|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>var foos = Foo.Where&lt;br&gt;
( f =&gt; FooBar.Where(fb.BarId == 1000).Select(fb =&gt; fb.FooId).Contains(f.FooId));
</code></pre>


blocks|key|1770818|text|//先创建字典/+Set+/采集fids|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1770819|Find+Other+Artilces|offset|length|1770820|var+fids+=+(from+fb+in+FooBar
++++++++++++where+fb.BarID+=+1000
++++++++++++select+new+{+fooID+=+fb.FooID,+barID+=+fb.BarID+})
++++++++++++.ToDictionary(x+=>+x.fooID,+x+=>+x.barID);

from+f+in+Foo
where+fids.HasKey(f.FooId)
select+f|code-block|syntax|javascript|1770821|entityMap|0|LINK|mutability|MUTABLE|url|http://www.doyouknow.in/How.aspx^0|0|0|J|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@$D|U|E|V|1|W]]|A|$]]|$1|F|3|G|5|H|7|X|8|@]|9|@]|A|$I|J]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

<p>// create a Dictionary / Set / Collection fids first</p>

<p><a href="http://www.doyouknow.in/How.aspx" rel="nofollow noreferrer">Find Other Artilces</a></p>

<pre><code>var fids = (from fb in FooBar
            where fb.BarID = 1000
            select new { fooID = fb.FooID, barID = fb.BarID })
            .ToDictionary(x =&gt; x.fooID, x =&gt; x.barID);

from f in Foo
where fids.HasKey(f.FooId)
select f
</code></pre>


blocks|key|1770841|text|//先创建字典/+Set+/采集fids|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1770842|Find+Other+Artilces|offset|length|1770843|var+fids+=+(from+fb+in+FooBar+where+fb.BarID+=+1000+select+new+{+fooID+=+fb.FooID,+barID+=+fb.BarID+})+.ToDictionary(x+=>+x.fooID,+x+=>+x.barID);

from+f+in+Foo+where+fids.HasKey(f.FooId)+select+f|code-block|syntax|javascript|1770844|entityMap|0|LINK|mutability|MUTABLE|url|http://www.doyouknow.in/DoYouKnow/How.aspx^0|0|0|J|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@$D|U|E|V|1|W]]|A|$]]|$1|F|3|G|5|H|7|X|8|@]|9|@]|A|$I|J]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

<p>// create a Dictionary / Set / Collection fids first</p>

<p><a href="http://www.doyouknow.in/DoYouKnow/How.aspx" rel="nofollow noreferrer">Find Other Artilces</a></p>

<pre><code>var fids = (from fb in FooBar where fb.BarID = 1000 select new { fooID = fb.FooID, barID = fb.BarID }) .ToDictionary(x =&gt; x.fooID, x =&gt; x.barID);

from f in Foo where fids.HasKey(f.FooId) select f
</code></pre>


blocks|key|1555781|text|from+f+in+foo
where+f.FooID+equals+model.FooBar.SingleOrDefault(fBar+=>+fBar.barID+=+1000).FooID
select+new
{
f.Columns
};|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1555782|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>from f in foo
where f.FooID equals model.FooBar.SingleOrDefault(fBar =&gt; fBar.barID = 1000).FooID
select new
{
f.Columns
};
</code></pre>


<p>I'm a bit stuck on this. Basically I want to do something like the following SQL query in LINQ to SQL:</p>
<pre><code>SELECT f.* 
FROM Foo f
WHERE f.FooId IN (
    SELECT fb.FooId
    FROM FooBar fb
    WHERE fb.BarId = 1000
)
</code></pre>
<p>Any help would be gratefully received.</p>


How can you handle an IN sub-query with LINQ to SQL?

我有点卡在这上面了。基本上，我想在LINQ to SQL中执行类似以下SQL查询的操作：SELECT f.* FROM Foo fWHERE f.FooId IN (    SELECT fb.FooId    FROM FooBar fb    WHERE fb.BarId = 1000)我们将非常感谢您的帮助。

问如何使用LINQ to SQL处理IN子查询？
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