title: Entity Framework - Expecting non-empty string for 'providerInvariantName' parameter
body: <p>Ok, this may not be related to EF. I am trying to use the code-first feature and following is what I wrote:-</p>
  
  <pre><code>var modelBuilder = new ModelBuilder();
              var model = modelBuilder.CreateModel();
              using (AddressBook context = new AddressBook(model))
              {
                  var contact = new Contact
                  {
                      ContactID = 10000,
                      FirstName = "Brian",
                      LastName = "Lara",
                      ModifiedDate = DateTime.Now,
                      AddDate = DateTime.Now,
                      Title = "Mr."
  
                  };
                  context.contacts.Add(contact);
                  int result = context.SaveChanges();
                  Console.WriteLine("Result :- "+ result.ToString());
  
              }
  </code></pre>
  
  <p>The context class:-</p>
  
  <pre><code>public class AddressBook : DbContext
      {
          public AddressBook()
          { }
          public AddressBook(DbModel AddressBook)
              : base(AddressBook)
          {
  
          }
          public DbSet&lt;Contact&gt; contacts { get; set; }
          public DbSet&lt;Address&gt; Addresses { get; set; }
      }
  </code></pre>
  
  <p>and the connection string:-</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8" ?&gt;
  &lt;configuration&gt;
      &lt;connectionStrings&gt;
      &lt;add name="AddressBook"  connectionString="Data Source=MyMachine;Initial Catalog=AddressBook;Integrated Security=True;MultipleActiveResultSets=True;providerName=System.Data.SqlClient"/&gt;
      &lt;/connectionStrings&gt;
  &lt;/configuration&gt;
  </code></pre>
  
  <p>So, the database name is "AddressBook" and the error happens when I initialize the AddressBook object. I see people suggesting to add (providerName="System.Data.SqlClient") to the connection string. But It does not work in my case.  Am I missing anything here?</p>