Programmatically creating code first migrations

First of all, no way to run Nuget powershell outside visual studio (it uses DTE). Also, everything you write without Visual Studio need to be inserted in the csproj manually (but not an hard task).

Just to show how it works I send you some line of codes. To test them, create MyDll dll (a project test with context and entities) and then manually enabled migrations on MyDll with Enable-Migrations (just to create Configuration.cs).

After that you can use this piece of code to generate the source code

DbConnectionInfo connectionStringInfo = new DbConnectionInfo(
    "Server=.;Database=MigrationTest;User=sa;Password=dacambiare", "System.Data.SqlClient"); // We shoud retrieve this from App.config

ToolingFacade toolingFacade =  new ToolingFacade(
    "MyDll",   // MigrationAssemblyName. In this case dll should be located in "C:\\Temp\\MigrationTest" dir
    "MyDll",  // ContextAssemblyName. Same as above
    null,
    "C:\\Temp\\MigrationTest",   // Where the dlls are located
    "C:\\Temp\\MigrationTest\\App.config", // Insert the right directory and change with Web.config if required
    "C:\\Temp\\App_Data",
    connectionStringInfo)
{
    LogInfoDelegate = s => {Console.WriteLine(s);},
    LogWarningDelegate = s => { Console.WriteLine("WARNING: " + s); },
    LogVerboseDelegate = s => { Console.WriteLine("VERBOSE: " + s); }
};


ScaffoldedMigration scaffoldedMigration = toolingFacade.Scaffold("MyMigName", "C#", "MyAppNameSpace", false);

Console.WriteLine(scaffoldedMigration.DesignerCode);
Console.WriteLine("==================");
Console.WriteLine(scaffoldedMigration.UserCode);

// Don't forget the resource file that is in the scaffoldedMigration

EDIT
I forgot the namespaces and are not used often so here you are

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

Not a real answer to your question, rather share of my experience: I'd be very careful with migrations generated for you this way. A lot of times when I create migrations (in VS) I review them. I check if the proposed changes are what I want them to be and EF is not trying to do something stupid (like column/table renaming by dropping table and creating a new one).

Also sometimes EF is missing some critical changes - recently I had troubles generating correct migrations when I changed the lengths of nvarchar fields. This also required careful review of the migrations.

And your migrations are code as well. We are doing peer-reviews of migrations before they can go to production. Creating migrations automatically will make these changes less visible and can potentially cause a data loss in production.

And if you are struggling with migrations in team-environment - we've solved this by communication: every time when a developer checks in a new migration - emails is sent to all other devs on this project. Fixed all our problems.

Update Just had a discussion with a colleague and another issue came up - how would you do your local development? Would you create migrations on dev's machine, make sure everything works? Then delete the migration and check-in the code? and then your CI will re-generate your migration? I think this will blow dev's minds when working with EF.

You can use the System.Data.Entity.Migrations.Design.MigrationScaffolder class to programmatically generate migrations like so:

[TestMethod]
public void GenerateTestMigration()
{
    var config = new MyDbMigrationsConfiguration();
    var scaffolder = new MigrationScaffolder(config);
    var pendingMigration = scaffolder.Scaffold("TestMigration");
    Trace.WriteLine(pendingMigration.UserCode);
}

I use this and other techniques on our build server to fail the build if there are pending migrations or if a migration needs to be created like so:

using Microsoft.VisualStudio.TestTools.UnitTesting;
using System.Data.Entity.Migrations;
using System.Data.Entity.Migrations.Design;
using System.Diagnostics;
using System.Linq;

namespace YabbaDabbaDoo
{
    [TestClass]
    public class MigrationTests
    {
        [TestMethod]
        [TestCategory("RunOnBuild")]
        public void VerifyThereAreNoPendingMigrations()
        {
            // Arrange
            var config = new MyDbMigrationsConfiguration();
            var dbMigrator = new DbMigrator(config);

            // Act
            var pendingMigrations = dbMigrator.GetPendingMigrations().ToList();

            // Visual Assertion
            Trace.WriteLine(pendingMigrations);

            // Assert
            Assert.AreEqual(0, pendingMigrations.Count(), "There are pending EF migrations that need to be ran.");
        }

        [TestMethod]
        [TestCategory("RunOnBuild")]
        public void VerifyDatabaseIsCompatibleWithModel()
        {
            // Arrange
            var context = new MyDbContext();

            // Act
            var isCompatible = context.Database.CompatibleWithModel(false);

            // Visual Assertion
            if (!isCompatible)
            {
                var config = new MyDbMigrationsConfiguration();
                var scaffolder = new MigrationScaffolder(config);
                var pendingMigration = scaffolder.Scaffold("MissingMigration");

                Trace.WriteLine("Missing Migration:");
                Trace.WriteLine("");
                Trace.WriteLine(pendingMigration.UserCode);
            }

            // Assert
            Assert.IsTrue(isCompatible, "The EF model is not compatible with the database. An EF migration needs to be created. See output for sample of missing migration.");
        }
    }
}