Manually Provide DbContext to DbMigrator

Platform .NET 4.5 and Entity Framework 6.

Question I have the following code to execute a Migration:

//The following function just returns an object of the Configuration() class 
//generated by code migrations
var migratorConfig = currentMigrationProvider.CreateDbMigrationConfiguration(); 
var dbMigrator = new System.Data.Entity.Migrations.DbMigrator(migratorConfig);
dbMigrator.Update();

The problem is that Update() function tries to create an instance of my DbContext class and for a few good reasons I need to manually create the context and feed it to dbMigrator. Is that possible? How?

Yes it is possible to control migrations and the context. This is important if you are managing the connection. The example shows connecting to 2 different Dbs. It is a little convoluted. So i built a little test project to demo how.

using System;
using System.Data.Common;
using System.Data.Entity;
using System.Data.Entity.Infrastructure;
using System.Data.Entity.Migrations;

namespace Ef6Test {
public class Program {
    public static void Main(string[] args) {
        ExecDb1();
        ExecDB2();
       ExecDbCtx3();
    }

    private static void ExecDb1() {
        Database.SetInitializer(new MigrateDatabaseToLatestVersion<Ef6Ctx, Ef6MigConf>());
        WhichDb.DbName = "HACKDB1";
        WhichDb.ConnType = ConnType.CtxViaDbConn;
        var sqlConn = GetSqlConn4DBName(WhichDb.DbName);
        var context = new Ef6Ctx(sqlConn);
        context.Database.Initialize(true);
        Console.WriteLine(WhichDb.DbName, context.Database.Exists() );
        AddJunk(context);
        //sqlConn.Close();  //?? whatever other considerations, dispose of context etc...
    }

    private static void ExecDB2() {
        // yes other its default again reset this !!!!
        WhichDb.DbName = "HACKDB2";
        WhichDb.ConnType = ConnType.CtxViaDbConn;
        var sqlConn2 = GetSqlConn4DBName(WhichDb.DbName);
        var context2 = new Ef6Ctx2(sqlConn2);
        Console.WriteLine(context2.Database.Exists());
        Database.SetInitializer(new MigrateDatabaseToLatestVersion<Ef6Ctx2, Ef6MigConf2>());
        context2.Database.Initialize(true);
        Console.WriteLine(WhichDb.DbName, context2.Database.Exists());
        AddJunk(context2);
    }

    private static void ExecDbCtx3() {
        Database.SetInitializer(new MigrateDatabaseToLatestVersion<Ef6Ctx3, Ef6MigConf3>());
        // Database.SetInitializer(new CreateDatabaseIfNotExists<Ef6Ctx3>());
        // Database.SetInitializer(null);
        WhichDb.ConnectionName = "AppCfgName";
        WhichDb.ConnType = ConnType.CtxViaConnectionName;

        var context3 = new Ef6Ctx3(WhichDb.ConnectionName);
        context3.Database.Initialize(true);
        Console.WriteLine(WhichDb.ConnectionName, context3.Database.Exists());
        AddJunk(context3);
    }


    public static class WhichDb {
        public static string DbName { get; set; }
        public static string ConnectionName { get; set; }
        public static ConnType ConnType { get; set; }
    }

    public enum ConnType {
        CtxViaDbConn,
        CtxViaConnectionName
    }

    private static void AddJunk(DbContext context) {
        var poco = new pocotest();
        poco.f1 = DateTime.Now.ToString();
        //  poco.f2 = "Did somebody step on a duck?";  //comment in for second run
        context.Set<pocotest>().Add(poco);
        context.SaveChanges();
    }

    public static DbConnection GetSqlConn4DBName(string dbName) {
        var sqlConnFact = new SqlConnectionFactory(
            "Data Source=localhost; Integrated Security=True; MultipleActiveResultSets=True");
        var sqlConn = sqlConnFact.CreateConnection(dbName);
        return sqlConn;
    }
}

public class MigrationsContextFactory : IDbContextFactory<Ef6Ctx> {
    public Ef6Ctx Create() {
        switch (Program.WhichDb.ConnType) {
            case Program.ConnType.CtxViaDbConn:
                var sqlConn = Program.GetSqlConn4DBName(Program.WhichDb.DbName); // NASTY but it works
                return new Ef6Ctx(sqlConn);

            case Program.ConnType.CtxViaConnectionName:
                return new Ef6Ctx(Program.WhichDb.ConnectionName);
            default:
                throw new ArgumentOutOfRangeException();
        }
    }
}

public class MigrationsContextFactory2 : IDbContextFactory<Ef6Ctx2> {
    public Ef6Ctx2 Create() {
        switch (Program.WhichDb.ConnType) {
            case Program.ConnType.CtxViaDbConn:
                var sqlConn = Program.GetSqlConn4DBName(Program.WhichDb.DbName); // NASTY but it works
                return new Ef6Ctx2(sqlConn);

            case Program.ConnType.CtxViaConnectionName:
                return new Ef6Ctx2(Program.WhichDb.ConnectionName);
            default:
                throw new ArgumentOutOfRangeException();
        }
    }
}

public class MigrationsContextFactory3 : IDbContextFactory<Ef6Ctx3> {
    public Ef6Ctx3 Create() {
        switch (Program.WhichDb.ConnType) {
            case Program.ConnType.CtxViaDbConn:
                var sqlConn = Program.GetSqlConn4DBName(Program.WhichDb.DbName); // NASTY but it works
                return new Ef6Ctx3(sqlConn);

            case Program.ConnType.CtxViaConnectionName:
                return new Ef6Ctx3(Program.WhichDb.ConnectionName);
            default:
                throw new ArgumentOutOfRangeException();
        }
    }
 }

public class Ef6MigConf : DbMigrationsConfiguration<Ef6Ctx> {
    public Ef6MigConf() {
        AutomaticMigrationsEnabled = true;
        AutomaticMigrationDataLossAllowed = true;
    }
 }

public class Ef6MigConf2 : DbMigrationsConfiguration<Ef6Ctx2> {
    public Ef6MigConf2() {
        AutomaticMigrationsEnabled = true;
        AutomaticMigrationDataLossAllowed = true;
    }
 }

 public class Ef6MigConf3 : DbMigrationsConfiguration<Ef6Ctx3> {
    public Ef6MigConf3() {
        AutomaticMigrationsEnabled = true;
        AutomaticMigrationDataLossAllowed = true;
    }
}

public class pocotest {
    public int Id { get; set; }
    public string f1 { get; set; }
 public string f2 { get; set; } // comment in for second run
 public string f2a { get; set; } // comment in for second run
  public string f3 { get; set; } // comment in for second run
 public string f5 { get; set; } // comment in for second run
 public string f6b { get; set; } // comment in for second run
}

public class Ef6Ctx : DbContext {
    public Ef6Ctx(DbConnection dbConn) : base(dbConn, true) { }

    public Ef6Ctx(string connectionName) : base(connectionName) { }

    public DbSet<pocotest> poco1s { get; set; }
}

public class Ef6Ctx2 : DbContext {
    public Ef6Ctx2(DbConnection dbConn) : base(dbConn, true) { }
    public Ef6Ctx2(string connectionName) : base(connectionName) { }
    public DbSet<pocotest> poco1s { get; set; }
}
}