title: Object reference not set to an instance of an object - C#
body: <p>I'm a beginner to c# and I keep getting a 'System.NullReferenceException' error. I've looked everywhere but I can't seem to find a useful solution. 
  I simplified the code below so that it would be more clear.</p>
  
  <pre><code>namespace tile_test
  {
      public class Game1 : Game
      {
          public static float bottomWorld = 38400f;
          public static float rightWorld = 134400f;
          public static int maxTilesX = (int)rightWorld / 16 + 1;
          public static int maxTilesY = (int)bottomWorld / 16 + 1;
  
  
          public Game1()
          {
              Tile[,] tile = new Tile[maxTilesX, maxTilesY];
              int x = 1;
              int y = 1;
              tile[x, y].active = false; //Error on this line.
          }
      }
  }
  </code></pre>
  
  <p>The Tile-class is shown below</p>
  
  <pre><code>namespace tile_test
  {
      public class Tile
      {
          public bool active;
      }
  }
  </code></pre>
  
  <p>Could anyone help me out?</p>