Скачать или смотреть How to Create a Database with __MigrationHistory in EF Core 6

Learn how to set up an initial database for development using Entity Framework Core 6, ensuring that your migration history is correctly tracked.
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How to Create a Database with __MigrationHistory in EF Core 6

When working with Entity Framework (EF) Core 6, especially with an existing database, you might encounter challenges with migration history. This scenario commonly arises if you've made changes to your existing database and need to manage those changes effectively through migrations. If you find yourself asking, "How can I create an initial database for development purposes on my local machine?", you’re not alone! Let's delve into the solution step-by-step.

Understanding the Issue

Many developers face the issue of creating tables in a new local database while ensuring that migration history is properly maintained. If you directly attempt to create tables without a migration history, subsequent migrations may fail. Typically, the problem arises in two ways:

Creating Tables without Migration History: If you create tables using the CreateTablesAsync method, your migration information will not be available, leading to failure in later migrations.

Running Empty Migrations: When executing an empty migration with MigrateAsync, while it won't create any tables, it also fails to add the necessary migration record in your __MigrationHistory table.

The Solution: Initial Migration Setup

Instead of trying to create an empty migration, a more effective approach would be to generate a complete initial migration based on your current model. Here’s how you can achieve this step-by-step:

Step 1: Generate a Full Initial Migration

In your project, use the EF Core tools to generate a new migration that reflects your current model.

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This migration will not be empty; it will contain all the necessary schema changes for your existing database.

Step 2: Migrate the Local Database

Now, you can migrate this initial migration to your local database. Use your DbContext to call MigrateAsync:

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This operation will apply the migration, create your tables, and also populate your __MigrationHistory table.

Step 3: Sync Migration History with Production Database

To ensure that your production database recognizes this initial migration and skips it when updating, you will need to transfer the relevant migration history.

Create a backup of the row from your local __MigrationHistory table that corresponds to this initial migration.

Insert this row into the production database’s __MigrationHistory table.

Additional Considerations

Schema Changes: Ensure that any schema modifications are carefully reviewed and tested on your local database.

Development vs. Production: Always differentiate between development and production environments to prevent accidentally applying incorrect migrations.

Conclusion

By following this outlined approach, you can effectively create an initial database for development in EF Core 6 while maintaining a proper migration history. This method not only ensures that you have a working local database but also sets you up well for future changes without the risk of migration conflicts.

Remember, the key takeaway is to generate a full initial migration based on your current model instead of starting with an empty migration to prevent issues with the migration history.

If you have any questions or need further clarification, feel free to reach out! Happy coding!