title: linq query for selecting from one list based on another
body: <pre><code>public class Test
  {
    int i;
    string s;
  }
  
  List&lt;Test&gt; testList = new List&lt;Test&gt;(); //assume there are some values in it.
  
  List&lt;int&gt; intList = new List&lt;int&gt;(){ 1,2,3};
  </code></pre>
  
  <p>How to I say get <code>items from testList where i is in intList</code> using the linq to objects.</p>
  
  <p>something like <code>List&lt;Test&gt; testIntList = testList.Where(t=&gt;t.i in intList)</code></p>