Creating a Connection String and Working with SQL Server LocalDB

The MovieDBContext class you created handles the task of connecting to the database and mapping Movie objects to database records.

SQL Server Express LocalDB

LocalDB is a lightweight version of the SQL Server Express Database Engine that starts on demand and runs in user mode. LocalDB runs in a special execution mode of SQL Server Express that enables you to work with databases as .mdf files. Typically, LocalDB database files are kept in the App_Data folder of a web project.

SQL Server Express is not recommended for use in production web applications. LocalDB in particular should not be used for production with a web application because it is not designed to work with IIS. However, a LocalDB database can be easily migrated to SQL Server or SQL Azure. In Visual Studio 2017, LocalDB is installed by default with Visual Studio.By default, the Entity Framework looks for a connection string named the same as the object context class (MovieDBContext for this project).

Open the application root Web.config file shown below. (Not the Web.config file in the Views folder.)

Find the element:

Add the following connection string to the element in the Web.config file.

The following example shows a portion of the Web.config file with the new connection string added:

The two connection strings are very similar. The first connection string is named DefaultConnection and is used for the membership database to control who can access the application. The connection string you've added specifies a LocalDB database named Movie.mdf located in the App_Data folder. The name of the connection string must match the name of the DbContext class.

You don't actually need to add the MovieDBContext connection string. If you don't specify a connection string, Entity Framework will create a LocalDB database in the users directory with the fully qualified name of the DbContext class (in this case MvcMovie.Models.MovieDBContext). You can name the database anything you like, as long as it has the .MDF suffix. For example, we could name the database MyFilms.mdf.

All source collected from https://learn.microsoft.com/en-us/aspnet/mvc/overview/getting-started/introduction/creating-a-connection-string