title: How to check if a list of base type contains at least one instance of some child types
body: <p>I have a list of base class like this:</p>
  
  <pre><code>List&lt;BaseClass&gt; ChildClasses
  </code></pre>
  
  <p>I have child classes like this:</p>
  
  <pre><code>class ChildFoo : BaseClass {}
  class ChildBar : BaseClass {}
  class ChildBaz : BaseClass {}
  class ChildQax : BaseClass {}
  class ChildBox : BaseClass {}
  ...
  </code></pre>
  
  <p>I need to implement a method which can query the <code>ChildClasses</code> list to see if it has all of the types I pass to it, which are all derived from <code>BaseClass</code>.</p>
  
  <p>So, if I call this method for types <code>ChildFoo</code> and <code>ChildBar</code>, it should return true if <code>ChildClasses</code> list contains at least one instance of <code>ChildFoo</code> and <code>ChildBar</code>.</p>
  
  <p>How can I approach this situation?</p>