实体框架迁移-自动创建表和更新

Question

I maybe not understanding Migrations, but I am updating my opensource application to use them. My goal was

1) When a users runs the application for the first time with a blank database, the application auto creates the tables (And hits my seed method to auto populate required data).

2) If I add any new properties to my Entity/Model classes, they are auto added when the database.

Is it possible to do this without using the Nuget commands? As I was hoping this would take away a lot of my installer code for initially creating tables and adding data on first install.

I have the following set up

Database.SetInitializer(new MigrateDatabaseToLatestVersion<MVCForumContext, Migrations.Configuration>(AppConstants.MvcForumContext));

And my configuration class

internal sealed class Configuration : DbMigrationsConfiguration<MVCForumContext>
{
    public Configuration()
    {
        AutomaticMigrationsEnabled = true;
        AutomaticMigrationDataLossAllowed = false; 
    }

    protected override void Seed(MVCForumContext context)
    {
        //  This method will be called after migrating to the latest version.

        //  You can use the DbSet<T>.AddOrUpdate() helper extension method 
        //  to avoid creating duplicate seed data. E.g.
        //
        //    context.People.AddOrUpdate(
        //      p => p.FullName,
        //      new Person { FullName = "Andrew Peters" },
        //      new Person { FullName = "Brice Lambson" },
        //      new Person { FullName = "Rowan Miller" }
        //    );

        //TODO - ADD THE INITIAL DATA HERE
    }
}

And I have all my model classes mapped properly using the fluent API (ie)

public class BadgeMapping : EntityTypeConfiguration<Badge>
{
    public BadgeMapping()
    {
        HasKey(x => x.Id);

        Property(x => x.Id).IsRequired();
        Property(x => x.Name).IsRequired().HasMaxLength(50);
        Property(x => x.Description).IsOptional();
        Property(x => x.Type).IsRequired().HasMaxLength(50);
        Property(x => x.Image).IsOptional().HasMaxLength(50);
        Property(x => x.DisplayName).IsRequired().HasMaxLength(50);
        Property(x => x.AwardsPoints).IsOptional();

        // Ignores
        Ignore(x => x.Milestone);
    }
}

Again, I may be mis-understanding. But I created a blank database and ran the app pointing at the database.

It failed to create the tables with all the fields as I suspected? Am I missing something here?

I have been developing against an existing database, and to get it working I found a blog post outlining what you need to do to get it working with an existing database.

Simply run the add-migration initial command in the package manager console window, browse to the Migrations folder, modify the new file that has been added, it will contain a class that inhereits DbMigration, with two methods, Up and Down. If you remove all of the content of the methods, but leave the methods, then run the Update-Database -Verbose command in the package manager console it will work.

So I have cleared the UP() and Down() methods. If I put those back, then I can't run against an existing database.

Maybe it's just me thinking it's going to be smarter than I thought. Knowing to create tables if needed and auto update missing fields based on the model mappings?

Answer 1

You need to use add-migration every time when you change your model classes. When you run app for the first time after changes new migrations are applied to you database. With first migration your database gets the MigrationHistory table and then it is being used for checking which migrations have been applied and which need to be applied.