title: Parameter of OfType<????> when used in a method with C#
body: <p>I have this code to get "A" as a filtered result. </p>
  
  <pre><code>public static void RunSnippet()
  {
      Base xbase = new Base(); 
      A a = new A(); 
      B b = new B();
      IEnumerable&lt;Base&gt; list = new List&lt;Base&gt;() { xbase, a, b };
      Base f = list.OfType&lt;A&gt;().FirstOrDefault();
      Console.WriteLine(f);
  }
  </code></pre>
  
  <p>I need to use <code>IEnumerable&lt;Base&gt; list = new List&lt;Base&gt;() {xbase, a, b};</code> from a function as follows:</p>
  
  <pre><code>public static Base Method(IEnumerable&lt;Base&gt; list, Base b (????)) // I'm not sure I need Base b parameter for this?
  {
      Base f = list.OfType&lt;????&gt;().FirstOrDefault();
      return f;
  }
  
  public static void RunSnippet()
  {
      Base xbase = new Base(); 
      A a = new A(); 
      B b = new B();
      IEnumerable&lt;Base&gt; list = new List&lt;Base&gt;() { xbase, a, b };
      //Base f = list.OfType&lt;A&gt;().FirstOrDefault();
      Base f = Method(list);
      Console.WriteLine(f);
  }
  </code></pre>
  
  <p>What parameter do I use in '????' to get the same result from the original code? </p>