title: Converting int to int64, int variable still returning negative at int.MaxValue
body: <p>I'm trying to display the price of an item.  The price is multiplied by the item quantity.</p>
  
  <pre><code>int itemCost = itemPrice * itemQuanity;
  </code></pre>
  
  <p>When the quantity of the item becomes too much, the itemCost goes into negatives, meaning I need a larger int, so I changed the int to use int64.</p>
  
  <pre><code>int64 itemCost = itemPrice * itemQuantity;
  </code></pre>
  
  <p>With this change it still outputs a negative itemCost, what am I doing wrong?</p>
  
  <p>I tried using</p>
  
  <pre><code>System.Convert.ToInt64(int value);
  </code></pre>
  
  <p>but that doesn't seem to work either, still getting a negative number when reaching int.MaxValue.</p>