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Create and Drop APIs

  • Artikkeli

The EnsureCreated() and EnsureDeleted() methods provide a lightweight alternative to Migrations for managing the database schema. These methods are useful in scenarios when the data is transient and can be dropped when the schema changes. For example during prototyping, in tests, or for local caches.

Some providers (especially non-relational ones) don't support Migrations. For these providers, EnsureCreated is often the easiest way to initialize the database schema.

Warning

EnsureCreated and Migrations don't work well together. If you're using Migrations, don't use EnsureCreated to initialize the schema.

Transitioning from EnsureCreated to Migrations is not a seamless experience. The simplest way to do it is to drop the database and re-create it using Migrations. If you anticipate using migrations in the future, it's best to just start with Migrations instead of using EnsureCreated.

EnsureDeleted

The EnsureDeleted method will drop the database if it exists. If you don't have the appropriate permissions, an exception is thrown.

// Drop the database if it exists
dbContext.Database.EnsureDeleted();

EnsureCreated

EnsureCreated will create the database if it doesn't exist and initialize the database schema. If any tables exist (including tables for another DbContext class), the schema won't be initialized.

// Create the database if it doesn't exist
dbContext.Database.EnsureCreated();

Tip

Async versions of these methods are also available.

SQL Script

To get the SQL used by EnsureCreated, you can use the GenerateCreateScript method.

var sql = dbContext.Database.GenerateCreateScript();

Multiple DbContext classes

EnsureCreated only works when no tables are present in the database. If needed, you can write your own check to see if the schema needs to be initialized, and use the underlying IRelationalDatabaseCreator service to initialize the schema.

// TODO: Check whether the schema needs to be initialized

// Initialize the schema for this DbContext
var databaseCreator = dbContext.GetService<IRelationalDatabaseCreator>();
databaseCreator.CreateTables();