getting DesignTimeDbContextFactory to run migrations without executing Startup

Question

In my ASP.Net core application, Startup class has many things that is not needed to do migrations. According to This it seems I can create a DesignTimeFactory which will prepare the specified context and use it for migration purposes.

So I have created the simple class implementing IDesignTimeDbContextFactory which will simply accept a parameter, do some work with it and then return the MigrationContext for rest of the work within CreateDbContext(string[] args).

My problem is when I run Add-Migration commands from the console, it still executes StartUp class. . I thought with DesignTimeFactory, it shouldn't try to wire-up everything but simply use the context returned by the factory and use it for migration purposes.

Is there a way to avoid executing Startup class

       public static IHostBuilder CreateHostBuilder(string[] args) =>
        Host.CreateDefaultBuilder(args)
            .ConfigureWebHostDefaults(webBuilder =>
            {
                Debugger.Launch();
                webBuilder.UseStartup<Startup>();
            });

and simply rely only on the DBContextFactory for migration? So Startup class is only executing at run time

Probably something is wrong with your class implementing `IDesignTimeDbContextFactory` which prevents EF Core finding/using it. Run `Add-Migration` with `-Verbose` option and see/post the output. — Ivan Stoev, Jan 02 '21 at 13:13

score 0 · Accepted Answer · answered Jan 02 '21 at 14:49

Actually this has been in discussion at various levels. See this thread

So basically I renamed the CreateHostBuilder(string[] args) method name to PrepareHostBuilder(string[] args) and DesignTimeFactory stopped trying to wireup Startup stuff.

In the above URL, there is a detailed discussion going on about this.

score 0 · Answer 2 · answered Feb 10 '22 at 17:46

Since the EF cli supports command line arguments, a hack-ish work around is to pass in an arg of some kind to the Add-Migration or Update-Database command and check for its existence in the CreateHostBuilder(string[] args) method:

public static IHostBuilder CreateHostBuilder(string[] args) =>
    Host.CreateDefaultBuilder(args).ConfigureWebHostDefaults(webBuilder =>
    {
        if (!args.Contains("design"))
            webBuilder.UseStartup<Startup>();
    });

And then you could call the following command in PackageManagerConsole to skip the Startup file:

PM> Update-Database -Context MyContext -Args "design"

getting DesignTimeDbContextFactory to run migrations without executing Startup

2 Answers2