Connect multipal database by using connection string in MVC

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MVC4

i have 5 database with same table.i have situation like i have one login form in that we have to select Company Name from dropdown that company information like name userid password and other fields are taken from other database and other fields in login form are branch name,financial year, username, password that are verify by other database.Now first user select the company name then it verify the company name by using connection string by using userid and password after that it go to verify the all other fields from database. how to connect multiple database how to verify the connection string from dropdown.and after that all other field access the other connection field

What I have tried:

creates the connection string in web.config