title: Change DbContext connection at run-time
body: <p>I have 3 DBs that I want to work with: A,B and C.
  each one have the same tables (for example: users, products).</p>
  
  <p>I want to let the user decide (on run-time) which DB he wants to work with.
  So... I used EF5 and created 3 edbx files which created the following classes: ADBEntities, BDBEntities and CDBEntities.</p>
  
  <p>How can I let him decide the selecteddb so I could get its users?</p>
  
  <p>I mean,</p>
  
  <pre><code>var dstuff = from user in selecteddb.users
               where user.UserEmail == userEmail
               select user.UserID;
  </code></pre>
  
  <p>I've thought of using reflection / base class (DBEntities), but didn't get far with those ideas.</p>