MVC Controller for Scaffoldings

Hello,

Under Models, I added "Ado.Net Entity data model" so that I can create CRUD on 1 database table. On the Entity Data Model Wizard, I selected my existing database connection string in my web.config file. I didn't want to create a new connection string because there is no point to have more than one. Everything is fine and I completed the wizard. I then went to the Controller folder to create "Scaffoldings" for the CRUD. However, this process doesn't allow me to select the same existing connection string. The dropdown option doesn't list it on the wizard.

Would someone please give me some pointer on how to solve this? Where did I go wrong? Thank you.