Sample for Migrations with Multiple Providers does not work

[aleksandar-smilevski]

I was following the documentation for migrations with multiple providers and stumbled upon an issue.

I was trying to create migrations for multiple providers using one context type and used the sample provided.

If I run dotnet ef database update or dotnet ef database update -- --provider SqlServer from the WorkerService1 directory, the databases get updated/created.

However, if I try to do this programmatically using db.Database.Migrate() for instance here in Worker.cs, I get the following exception

An exception of type 'System.IO.FileNotFoundException' occurred in System.Private.CoreLib.dll but was not handled in user code: 'Could not load file or assembly 'SqliteMigrations, Culture=neutral, PublicKeyToken=null'. The system cannot find the file specified.'
   at System.Reflection.RuntimeAssembly.InternalLoad(ObjectHandleOnStack assemblyName, ObjectHandleOnStack requestingAssembly, StackCrawlMarkHandle stackMark, Boolean throwOnFileNotFound, ObjectHandleOnStack assemblyLoadContext, ObjectHandleOnStack retAssembly)
   at System.Reflection.RuntimeAssembly.InternalLoad(AssemblyName assemblyName, RuntimeAssembly requestingAssembly, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, AssemblyLoadContext assemblyLoadContext)
   at System.Reflection.Assembly.Load(AssemblyName assemblyRef)
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsAssembly..ctor(ICurrentDbContext currentContext, IDbContextOptions options, IMigrationsIdGenerator idGenerator, IDiagnosticsLogger`1 logger)
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
   at System.Reflection.RuntimeConstructorInfo.Invoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitCache(ServiceCallSite callSite, RuntimeResolverContext context, ServiceProviderEngineScope serviceProviderEngine, RuntimeResolverLock lockType)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScopeCache(ServiceCallSite singletonCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitCache(ServiceCallSite callSite, RuntimeResolverContext context, ServiceProviderEngineScope serviceProviderEngine, RuntimeResolverLock lockType)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScopeCache(ServiceCallSite singletonCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.Resolve(ServiceCallSite callSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.DynamicServiceProviderEngine.<>c__DisplayClass1_0.<RealizeService>b__0(ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngine.GetService(Type serviceType, ServiceProviderEngineScope serviceProviderEngineScope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope.GetService(Type serviceType)
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetService[T](IServiceProvider provider)
   at Microsoft.EntityFrameworkCore.RelationalDatabaseFacadeExtensions.GetRelationalService[TService](IInfrastructure`1 databaseFacade)
   at Microsoft.EntityFrameworkCore.RelationalDatabaseFacadeExtensions.Migrate(DatabaseFacade databaseFacade)
   at WorkerService1.Worker.Execute() in /home/aleksandar/Projects/EntityFramework.Docs/samples/core/Schemas/TwoProjectMigrations/WorkerService1/Worker.cs:line 38
   at WorkerService1.Worker.<StartAsync>b__3_0(Object state) in /home/aleksandar/Projects/EntityFramework.Docs/samples/core/Schemas/TwoProjectMigrations/WorkerService1/Worker.cs:line 23
   at System.Threading.TimerQueueTimer.<>c.<.cctor>b__23_0(Object state)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)

---

EF Core version: 5.0.2
Database provider: Microsoft.EntityFrameworkCore.SqlServer + Microsoft.EntityFrameworkCore.Sqlite
Target framework: NET 5.0
Operating system: Ubuntu
IDE: VS Code

[AndriySvyryd]

cc: @bricelam

[bricelam]

This is because the runtime doesn't resolve assemblies from the output directory--it uses the .deps.json file. We have additional logic in the tools to handle this. We should consider probing for the migrations assembly when the runtime fails to load it.

[AndriySvyryd]

#18840 should fix this