title: Type or namespace List<> not found
body: <p>Fairly new to C#, I'm trying to set two arrays, then join the elements of both these arrays into a list.
  The code goes as follows:</p>
  
  <pre><code>using System;
  
  namespace CMP_1002
  {
      class Program
      {
          static void Main(string[] args)
          {
  
              int a, b;
  
              Console.WriteLine("Enter the size of first set:");                  //arrange first array's size
              a = Convert.ToInt32(Console.ReadLine());
  
              int[] firstArray = new int[a];                                      //define first array
  
              for (int i=0; i&lt;a ; i++){                                           //read and add each first array element
                  Console.WriteLine("Enter element:");
                  firstArray[i] = Convert.ToInt32(Console.ReadLine());
              }
  
              Console.WriteLine("Enter the size of second set:");                 //arrange second array's size
              b = Convert.ToInt32(Console.ReadLine());
  
              int[] secondArray = new int[b];                                     //define second array
  
              for (int i=0; i&lt;b ; i++){                                           //read and add each second array element
                  Console.WriteLine("Enter element:");
                  secondArray[i] = Convert.ToInt32(Console.ReadLine());
              }
  
              List&lt;int&gt; union = new List&lt;int&gt;();                                  //define a new list for union
  
          }
      }
  }
  </code></pre>
  
  <p>Yet I've tried all the conventional ways to define a list; this is taken from MSDN. Every time the error pops up claiming "The type or namespace name 'List&lt;>' could not be found(are you missing a using directive or an assembly reference?)</p>
  
  <p>The code is written in Visual Studio 2017 for Mac Community Edition.</p>