Entity Framework allows a number of settings to be specified from the configuration file. In general EF follows a ‘convention over configuration’ principle. All the settings discussed in this post have a default behavior, you only need to worry about changing the setting when the default no longer satisfies your requirements.

All of these settings can also be applied using code. The configuration file option allows these settings to be easily changed during deployment without updating your code.

The Entity Framework Configuration Section

Starting with EF4.1 you could set the database initializer for a context using the appSettings section of the configuration file. In EF 4.3 we introduced the custom entityFramework section to handle the new settings. Entity Framework will still recognize database initializers set using the old format, but we recommend moving to the new format where possible.

The entityFramework section was automatically added to the configuration file of your project when you installed the EntityFramework NuGet package.

Connection Strings

This page provides more details on how Entity Framework determines the database to be used, including connection strings in the configuration file.

Connection strings go in the standard connectionStrings element and do not require the entityFramework section.

Code First based models use normal ADO.NET connection strings. For example:

EF Designer based models use special EF connection strings. For example:

Code First Default Connection Factory

The configuration section allows you to specify a default connection factory that Code First should use to locate a database to use for a context. The default connection factory is only used when no connection string has been added to the configuration file for a context.

When you installed the EF NuGet package a default connection factory was registered that points to either SQL Express or LocalDb, depending on which one you have installed.

To set a connection factory, you specify the assembly qualified type name in the deafultConnectionFactory element.
Note:An assembly qualified name is the namespace qualified name, followed by a comma, then the assembly that the type resides in. You can optionally also specify the assembly version, culture and public key token.

Here is an example of setting your own default connection factory:

The above example requires the custom factory to have a parameterless constructor. If needed, you can specify constructor parameters using the parameters element.

For example, the SqlCeConnectionFactory, that is included in Entity Framework, requires you to supply a provider invariant name to the constructor. The provider invariant name identifies the version of SQL Compact you want to use. The following configuration will cause contexts to use SQL Compact version 4.0 by default.

If you don’t set a default connection factory, Code First uses the SqlConnectionFactory, pointing to .\SQLEXPRESS. SqlConnectionFactory also has a constructor that allows you to override parts of the connection string. If you want to use a SQL Server instance other than .\SQLEXPRESS you can use this constructor to set the server.

The following configuration will cause Code First to use MyDatabaseServer for contexts that don’t have an explicit connection string set.

By default, it’s assumed that constructor arguments are of type string. You can use the type attribute to change this.

Database Initializers

Database initializers are configured on a per-context basis. They can be set in the configuration file using the context element. This element uses the assembly qualified name to identify the context being configured.

By default, Code First contexts are configured to use the CreateDatabaseIfNotExists initializer. There is a disableDatabaseInitialization attribute on the context element that can be used to disable database initialization.

For example, the following configuration disables database initialization for the Blogging.BlogContext context defined in MyAssembly.dll.

You can use the databaseInitializer element to set a custom initializer.

Constructor parameters use the same syntax as default connection factories.

You can configure one of the generic database initializers that are included in Entity Framework. The type attribute uses the .NET Framework format for generic types.

For example, if you are using Code First Migrations, you can configure the database to be migrated automatically using the MigrateDatabaseToLatestVersion<TContext, TMigrationsConfiguration> initializer.