Upgrade .mdf files
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This topic describes your options for upgrading your database file (.mdf) after you install a newer version of Visual Studio. It includes instructions for the following tasks:
Upgrade a database file to use a newer version of SQL Server Express LocalDB
Upgrade a database file to use a newer version of SQL Server Express
Work with a database file in Visual Studio but retain compatibility with an older version of SQL Server Express or LocalDB
Make SQL Server Express the default database engine
You can use Visual Studio to open a project that contains a database file (.mdf) that was created by using an older version of SQL Server Express or LocalDB. However, to continue to develop your project in Visual Studio, you must have that version of SQL Server Express or LocalDB installed on the same machine as Visual Studio, or you must upgrade the database file. If you upgrade the database file, you won't be able to access it by using older versions of SQL Server Express or LocalDB.
You may also be prompted to upgrade a database file that was created through an earlier version of SQL Server Express or LocalDB if the version of the file isn't compatible with the instance of SQL Server Express or LocalDB that’s currently installed. To resolve the issue, Visual Studio will prompt you to upgrade the file.
We recommend that you back up the database file before you upgrade it.
If you upgrade an .mdf file that was created in LocalDB 2014 (V12) 32 bit to LocalDB 2016 (V13), you will not be able to open the file again in the 32-bit version of LocalDB. In Update 2, LocalDB V13 is 64 bit only.
Before you upgrade a database, consider the following criteria:
Don't upgrade if you want to work on your project in both an older version and a newer version of Visual Studio.
Don't upgrade if your application will be used in environments that use SQL Server Express rather than LocalDB.
Don't upgrade if your application uses remote connections, because LocalDB doesn't accept them.
Don't upgrade if your application relies on Internet Information Services (IIS).
Consider upgrading if you want to test database applications in a sandbox environment but don't want to administer a database.
To upgrade a database file
In Server Explorer, select the Connect to Database button.
In the Add Connection dialog box, specify the following information:
Microsoft SQL Server (SqlClient)
To use the default version:
(localdb)\MSSQLLocalDB. This will specify either ProjectV12 or ProjectV13, depending on which version of Visual Studio is installed and when the first LocalDB instance was created. The MSSQLLocalDB node in SQL Server Object Explorer shows which version it is pointing to.
To use a specific version:
(localdb)\ProjectsV13, where V12 is LocalDB 2014 and V13 is LocalDB 2016.
Attach a database file: The physical path of the primary .mdf file.
Logical Name: The name that you want to use with the file.
Select the OK button.
When you're prompted, select the Yes button to upgrade the file.
The database is upgraded, is attached to the LocalDB database engine, and is no longer compatible with the older version of LocalDB.
You can also modify a SQL Server Express connection to use LocalDB by opening the shortcut menu for the connection and then selecting Modify Connection. In the Modify Connection dialog box, change the server name to
(LocalDB)\MSSQLLocalDB. In the Advanced Properties dialog box, make sure that User Instance is set to False.
To upgrade to a newer version of SQL Server Express
On the shortcut menu for the connection to the database, select Modify Connection.
In the Modify Connection dialog box, select the Advanced button.
In the Advanced Properties dialog box, select the OK button without changing the server name.
The database file is upgraded to match the current version of SQL Server Express.
To work with the database in Visual Studio but retain compatibility with SQL Server Express
In Visual Studio, open the project without upgrading it.
To run the project, select the F5 key.
To edit the database, open the .mdf file in Solution Explorer, and expand the node in Server Explorer to work with your database.
To make SQL Server Express the default database engine
On the menu bar, select Tools > Options.
In the Options dialog box, expand the Data Tools options, and then select the Data Connections node.
In the SQL Server Instance Name text box, specify the name of the instance of SQL Server Express or LocalDB that you want to use. If the instance isn't named, specify
.\SQLEXPRESS or (localdb)\MSSQLLocalDB.
Select the OK button.
SQL Server Express will be the default database engine for your applications.