title: Using Interface variables
body: <p>I'm still trying to get a better understanding of Interfaces.  I know about what they are and how to implement them in classes.</p>
  
  <p>What I don't understand is when you create a variable that is of one of your Interface types:</p>
  
  <pre><code>IMyInterface somevariable;
  </code></pre>
  
  <p>Why would you do this?  I don't understand how IMyInterface can be used like a class...for example to call methods, so:</p>
  
  <pre><code>somevariable.CallSomeMethod();
  </code></pre>
  
  <p>Why would you use an IMyInterface variable to do this?</p>