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I manually created a class

 public class AddClientsTable : DbMigration, IMigrationMetadata { string IMigrationMetadata.Id { get { return "201611281757258_AddClientsTable"; } } string IMigrationMetadata.Source { get { return null; } } string IMigrationMetadata.Target { get { return "AddClientsTable-Migration"; } } public override void Up() { CreateTable("Clients", t => new { ClientId = t.Guid(name:"ClientId"), Name = t.String() }) .PrimaryKey( t => t.ClientId, "ClientId") .Index( t => t.ClientId, "PK_Clients", true); } public override void Down() { DropIndex("Clients", "PK_Clients"); DropTable("Clients"); } }

and i want to apply it via code-first migrations from code like this :

 var migration = new AddClientsTable(); migration.Up(); context.RunMigration(migration);

which I stole from here but when I run the code I'm getting this exception :

Unable to cast object of type 'System.Data.Entity.Migrations.Model.CreateIndexOperation' to type 'System.Data.Entity.Migrations.Model.HistoryOperation'.

HistoryOperation is the operation which updates __MigrationHistory table ? so How do I do that via code ?

Am I missing something or the EntityFrameowrk Update-Database command does more than what I'm aware of ?

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  • why exactly are you trying to do it by code again? Commented Nov 28, 2016 at 19:19
  • well, I don't use visual studio ( too slow on my very old machine ) to execute Update-Database command, I just use gvim to do code editing and I really want to be able to do Code-First Databse Migration just like that. Commented Nov 28, 2016 at 19:23
  • Do you have powershell? There are powershell commands for each of the database functions for entity-framework Commented Nov 28, 2016 at 19:31
  • yes, I'm on windows and I do have powershell, but the need for doing it in code comes from the fact that I need to apply same migrations on my users' machines so it'll be easier to migrate their local databases. Commented Nov 28, 2016 at 19:37
  • If you want to execute all new migrations using code first, try MigrateDatabaseToLatestVersion msdn.microsoft.com/en-us/library/… (sample here github.com/tym32167/arma3beclient/blob/master/src/…) Commented Nov 28, 2016 at 19:39

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It doesn't make sense to cherry pick a migration and run it, because the migrations are cumulative and must be run in sequence. As such, you'd be better to run the equivalent of update-database powershell command at application startup.

Here's some code we use to do that:

In the Configuration.cs class constructor (this file was made when you enable-migrations)

AutomaticMigrationsEnabled = false; AutomaticMigrationDataLossAllowed = false;

then at app startup call the following method:

public static void ApplyDatabaseMigrations() { //Configuration is the class created by Enable-Migrations DbMigrationsConfiguration dbMgConfig = new Configuration() { ContextType = typeof(MyDbContext) //+++++CHANGE ME+++++ }; using (var databaseContext = new MyDbContext()) //+++++CHANGE ME+++++ { try { var database = databaseContext.Database; var migrationConfiguration = dbMgConfig; migrationConfiguration.TargetDatabase = new DbConnectionInfo(database.Connection.ConnectionString, "System.Data.SqlClient"); var migrator = new DbMigrator(migrationConfiguration); migrator.Update(); } catch (AutomaticDataLossException adle) { dbMgConfig.AutomaticMigrationDataLossAllowed = true; var mg = new DbMigrator(dbMgConfig); var scriptor = new MigratorScriptingDecorator(mg); string script = scriptor.ScriptUpdate(null, null); throw new Exception(adle.Message + " : " + script); } } }
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2 Comments

Tried your solution but was faced with another problem, ` string IMigrationMetadata.Target { get { return "AddClientsTable-Migration"; } }` this field needs to be a Base64 of the model (?), how can I generate it from code or from powershell ? I'm thinking of using powershell from comand line to generate the migrations and applying them using yoyr snipppet of code.
@Abdelghani This is what the Add-Migration command is for. Good luck navigating migrations without it.

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