title: Add-Migration throws an SQL ConnectionString exception
body: <p>I have a working application to who's DAL I just added EF5 migrations. While using Enable-Migrations and Add-Migrations, I get the following error.</p>
  
  <pre><code>Add-Migration EnforeUniqueIndexes
  </code></pre>
  
  <blockquote>
    <p>System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---><br>
    System.TypeInitializationException: The type initializer for 'Parkalot.Database.Context' threw an exception. ---><br>
    System.ArgumentException: The argument 'nameOrConnectionString' cannot be null, empty or contain only white space.</p>
  </blockquote>
  
  <p>I suspect that it is trying to connect to the database but the connection is not defined in that project. It is defined in another assembly that acts as the BLL and passes the connection string to the DAL.</p>
  
  <p>I do not want to keep a copy of the connection string in the DAL (in app settings or in code) and am not sure how to fix this. Please advise.</p>
  
  <p><strong>UPDATE:</strong> This is multi-tenant SaaS application so the DAL needs to be invoked with different connection strings based on context.</p>