title: List<> cannot be used C#
body: <p>I have this error and I don't have any idea what's happening, I'm new learning C# and where I'm learning they use this:</p>
  
  <pre><code>using System;
  
  namespace AgentSmith
  {
      class AgentSmith_missions
      {
          public static void Main(string[] args)
          {
              double[] array = {1.1, 2.2, 3.3};
              List&lt;double&gt; times  = new List&lt;double&gt;();
              times.Add(4.20);
              times.Add(7.30);
              times.Insert(1, 9.35);
              var four = times.IndexOf(4.20);
              times.Remove(times[four]);
              double seven = times.Contains(7.30);
              string s = String.Join(", ", times);
              Console.WriteLine(s + seven);
         }
      }
  }
  </code></pre>
  
  <p>The console error is this:</p>
  
  <pre><code>/Users.../AgentSmith.cs(10,13): error CS0246: The type or namespace name 'List&lt;&gt;' could not be found (are you missing a using directive or an assembly reference?)    
  /Users.../AgentSmith.cs(10,39): error CS0246: The type or namespace name 'List&lt;&gt;' could not be found (are you missing a using directive or an assembly reference?)
  </code></pre>