title: ASP.net, adding objects to a session variable
body: <p>I'm trying to add an object(s) to a session variable across postbacks.  My code looks similar to the following.</p>
  
  <pre><code>  Supply sup =  Supplies.GetSupply(supplyItemID);
  
    Session["CartObjects"] += sup;
  </code></pre>
  
  <p>Now, the compiler throws an error saying that the "+=" operator cannot be used on type 'object' and 'Supply'.  Do I need to implement an interface on my Supply object that allows it to be added?  Is this possible or am I thinking about this in the completely wrong way.</p>