How to add a new code-first migration with a newly-generated database?

Question

I\'ve enabled code-first migrations on my entity framework project, and have added several migrations which do things like rename tables. However, I have now deleted the databa

Answer 1

This implementation does not need to manually maintain records to be inserted to __MigrationHistory. Migrations are determined from assembly specified.

Maybe this helps.

My thanks goes to @Jez for initial idea.

/// 

/// An implementation of IDatabaseInitializer that will:
/// 1. recreate database only if the database does not exist 
/// 2. actualize __MigrationHistory to match current model state (i.e. latest migration)
/// 
/// The type of the context.
public class CreateDatabaseIfNotExistsAndMigrateToLatest : CreateDatabaseIfNotExists
    where TContext : DbContext
{
    private readonly Assembly migrationsAssembly;

    /// 

    /// Gets the migration metadata for types retrieved from . Types must implement .
    /// 
    /// The assembly.
    /// 
    private static IEnumerable GetMigrationMetadata(Assembly assembly)
    {
        var types = assembly.GetTypes().Where(t => typeof(IMigrationMetadata).IsAssignableFrom(t));
        var migrationMetadata = new List();
        foreach (var type in types)
        {
            migrationMetadata.Add(
                (IMigrationMetadata)Activator.CreateInstance(type));
        }

        return migrationMetadata.OrderBy(m => m.Id);
    }

    /// 

    /// Gets the provider manifest token.
    /// 
    /// The db.
    /// 
    private static string GetProviderManifestToken(TContext db)
    {
        var connection = db.Database.Connection;
        var token = DbProviderServices.GetProviderServices(connection).GetProviderManifestToken(connection);

        return token;
    }

    /// 

    /// Gets the migration SQL generator. Currently it is .
    /// 
    /// 
    private static MigrationSqlGenerator GetMigrationSqlGenerator()
    {
        return new SqlServerMigrationSqlGenerator();
    }

    /// 

    /// Creates the operation for inserting into migration history. Operation is created for one .
    /// 
    /// The migration metadatum.
    /// 
    private static InsertHistoryOperation CreateInsertHistoryOperation(IMigrationMetadata migrationMetadatum)
    {
        var model = Convert.FromBase64String(migrationMetadatum.Target);

        var op = new InsertHistoryOperation(
            "__MigrationHistory",
            migrationMetadatum.Id,
            model,
            null);

        return op;
    }

    /// 

    /// Generates the SQL statements for inserting migration into history table.
    /// 
    /// The generator.
    /// The operation.
    /// The token.
    /// 
    private static IEnumerable GenerateInsertHistoryStatements(
        MigrationSqlGenerator generator,
        InsertHistoryOperation op,
        string token)
    {
        return generator.Generate(new[] { op }, token);
    }

    /// 

    /// Runs the SQL statements on database specified by  ().
    /// 
    /// The statements.
    /// The db.
    private static void RunSqlStatements(IEnumerable statements, TContext db)
    {
        foreach (var statement in statements)
        {
            db.Database.ExecuteSqlCommand(statement.Sql);
        }
    }

    /// 

    /// Initializes a new instance of the  class.
    /// 
    /// The migrations assembly.
    public CreateDatabaseIfNotExistsAndMigrateToLatest(Assembly migrationsAssembly)
    {
        this.migrationsAssembly = migrationsAssembly;
    }

    protected override void Seed(TContext context)
    {
        base.Seed(context);

        // Get migration metadata for migrationAssembly
        var migrationMetadata = GetMigrationMetadata(migrationsAssembly);

        // Crate DbContext
        var db = Activator.CreateInstance();
        // Remove newly created record in __MigrationHistory
        db.Database.ExecuteSqlCommand("DELETE FROM __MigrationHistory");

        // Get provider manifest token
        var token = GetProviderManifestToken(db);
        // Get sql generator
        var generator = GetMigrationSqlGenerator();

        foreach (var migrationMetadatum in migrationMetadata)
        {
            // Create history operation
            var op = CreateInsertHistoryOperation(migrationMetadatum);
            // Generate history insert statements
            var statements = GenerateInsertHistoryStatements(generator, op, token);
            // Run statements (SQL) over database (db)
            RunSqlStatements(statements, db);
        }
    }
}