If Program.Main calls extension methods, dotnet aspnet-codegenerator -dc fails with "Could not get the reflection type for DbContext"

[dylanbeattie]

The bug occurs when trying to run dotnet aspnet-codegenerator and specify a DbContext:

dotnet aspnet-codegenerator controller -name ArtistsController -m Artist -dc MyDbContext

If the application's Program.Main method calls any extension methods, the tool fails with:

Could not get the reflection type for DbContext : MyDbContext
  at Microsoft.VisualStudio.Web.CodeGeneration.ActionInvoker.<BuildCommandLine>b__6_0()
  at Microsoft.Extensions.CommandLineUtils.CommandLineApplication.Execute(String[] args)
  at Microsoft.VisualStudio.Web.CodeGeneration.ActionInvoker.Execute(String[] args)
  at Microsoft.VisualStudio.Web.CodeGeneration.CodeGenCommand.Execute(String[] args)

This happens with projects that reference Microsoft.VisualStudio.Web.CodeGeneration.Design v8.0.0. The same code works fine with Microsoft.VisualStudio.Web.CodeGeneration.Design v7.0.1, running under both .NET 7 and under .NET 8.

• Verified on .NET 8.0.101 Windows 10 Pro 10.0.19045
• Verified on .NET 8.0.101 on Linux (Ubuntu 20.04 on Windows WSL2)

Code is below, and there are .NET 7 and .NET 8 projects demonstrating the problem available at github.com/dylanbeattie/dotnet8-aspnet-codegenerator-bug.

using Microsoft.Data.Sqlite;
using Microsoft.EntityFrameworkCore;

var builder = WebApplication.CreateBuilder(args);

/* The codegen command that reproduces the problem:

 dotnet aspnet-codegenerator controller -name ArtistsController -m Artist -dc MyDbContext

If you uncomment the call to builder.DoNothing(), this command fails with:
  Could not get the reflection type for DbContext : MyDbContext
    at Microsoft.VisualStudio.Web.CodeGeneration.ActionInvoker.<BuildCommandLine>b__6_0()
    at Microsoft.Extensions.CommandLineUtils.CommandLineApplication.Execute(String[] args)
    at Microsoft.VisualStudio.Web.CodeGeneration.ActionInvoker.Execute(String[] args)
    at Microsoft.VisualStudio.Web.CodeGeneration.CodeGenCommand.Execute(String[] args)
*/

// builder.DoNothing();

builder.Services.AddControllersWithViews();
var sqliteConnection = new SqliteConnection("Data Source=:memory:");
sqliteConnection.Open();
builder.Services.AddDbContext<MyDbContext>(options => options.UseSqlite(sqliteConnection));
var app = builder.Build();


using (var scope = app.Services.CreateScope()) {
	var db = scope.ServiceProvider.GetService<MyDbContext>()!;
	db.Database.EnsureCreated();
}

app.UseStaticFiles();
app.UseRouting();
app.MapGet("/", (MyDbContext db) => db.Artists.ToList());
app.MapControllerRoute("default", "{controller=Home}/{action=Index}/{id?}");
app.Run();

public static class ExtensionMethods {
	public static bool DoNothing(this WebApplicationBuilder builder) => true;
}

public class Artist {
	public Guid Id { get; set; }
	public string Name { get; set; } = String.Empty;
}

public class MyDbContext : DbContext {
	public MyDbContext(DbContextOptions<MyDbContext> options) : base(options) { }

	public DbSet<Artist> Artists { get; set; } = default!;
	protected override void OnModelCreating(ModelBuilder modelBuilder) 	{
		base.OnModelCreating(modelBuilder);
		modelBuilder.Entity<Artist>().HasData(
			new Artist { Id = Guid.NewGuid(), Name = "Artist A" },
			new Artist { Id = Guid.NewGuid(), Name = "Artist B" },
			new Artist { Id = Guid.NewGuid(), Name = "Artist C" }
		);
	}
}

[dylanbeattie]

I'm guessing this is related to some other issues folks have reported with aspnet-codegenerator when specifying a DbContext:

• Cannot scaffold Identity due to ambiguous calls between extension methods. #2621
• Could not get the reflection type for DbContext when using DI #2604

[deepchoudhery]

Haven't gotten to fixing this bug, thanks a lot for finding this info, will have this fixed for servicing early next month.

[dylanbeattie]

I'm also seeing the same behaviour if I call any extension methods from within the DbContext.

Given this utility class:

public static class NodaTimeConverters {

	public static ModelConfigurationBuilder AddNodaTimeConverters(this ModelConfigurationBuilder builder) {
		builder.Properties<Instant>().HaveConversion<InstantToDateTimeOffsetConverter>();
		return builder;
	}

	private class InstantToDateTimeOffsetConverter()
		: ValueConverter<Instant, DateTimeOffset>(i => i.ToDateTimeOffset(),
			dto => Instant.FromDateTimeOffset(dto));
}

If I call the AddNodaTimeConverters as an extension method:

	protected override void ConfigureConventions(ModelConfigurationBuilder configurationBuilder) {
		base.ConfigureConventions(configurationBuilder);
		configurationBuilder.AddNodaTimeConverters();
	}

I get the same error "Could not get the reflection type for DbContext", but if I call the same code as a static method:

	protected override void ConfigureConventions(ModelConfigurationBuilder configurationBuilder) {
		base.ConfigureConventions(configurationBuilder);
		NodaTimeConverters.AddNodaTimeConverters(configurationBuilder);
	}

it works.

[Grizzlly]

@deepchoudhery any updates?