title: Remove an item in List if not exists in other list using linq
body: <p>I have two different types of Lists</p>
  
  <pre><code>class A
  
  {
  
  int number;
  
  string name;
  
  }
  
  class B
  
  {
  
  int number;
  
  }
  
  List&lt;A&gt; a1;
  
  List&lt;B&gt; b1;
  </code></pre>
  
  <p>And now both the lists were populated and now i want to remove items(number) in list a1 if that item(number) not exists in list b1.tried the below approach</p>
  
  <pre><code>a1.removeall(a=&gt;b1.Exists(b1.number!=a1.number);
  </code></pre>
  
  <p>but the result is not as expected.Please help me...</p>