Could not load type AdHocMapper after upgrading from 8 to 9

[rwb196884]

Unit test project using in memory database (Microsoft.EntityFrameworkCore.InMemory).

Working in net8.

Updated to net9 and updated packages and now it's stopped working.

Message: 
System.TypeLoadException : Could not load type 'Microsoft.EntityFrameworkCore.Metadata.Internal.AdHocMapper' from assembly 'Microsoft.EntityFrameworkCore, Version=9.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60'.

  Stack Trace: 
EntityFrameworkRelationalServicesBuilder.TryAddCoreServices()
SqlServerServiceCollectionExtensions.AddEntityFrameworkSqlServer(IServiceCollection serviceCollection)
SqlServerOptionsExtension.ApplyServices(IServiceCollection services)
ServiceProviderCache.ApplyServices(IDbContextOptions options, ServiceCollection services)
ServiceProviderCache.<GetOrAdd>g__BuildServiceProvider|4_1(IDbContextOptions _, ValueTuple`2 arguments)
<>c.<GetOrAdd>b__4_0(IDbContextOptions contextOptions, ValueTuple`2 tuples)
ConcurrentDictionary`2.GetOrAdd[TArg](TKey key, Func`3 valueFactory, TArg factoryArgument)
ServiceProviderCache.GetOrAdd(IDbContextOptions options, Boolean providerRequired)
DbContext.ctor(DbContextOptions options)
XxxDbContext.ctor(DbContextOptions`1 options) line 64
<26 more frames...>
DelegatedWebApplicationFactory.CreateHost(IHostBuilder builder)
WebApplicationFactory`1.ConfigureHostBuilder(IHostBuilder hostBuilder)
WebApplicationFactory`1.EnsureServer()
WebApplicationFactory`1.CreateDefaultClient(DelegatingHandler[] handlers)
WebApplicationFactory`1.CreateDefaultClient(Uri baseAddress, DelegatingHandler[] handlers)
WebApplicationFactory`1.CreateClient(WebApplicationFactoryClientOptions options)
TestBase.ctor(XxxWebApplicationFactory`1 factory, Boolean passTroughSecurity) line 54
SomeTests.ctor(XxxWebApplicationFactory`1 factory) line 13
InvokeStub_SomeTests.ctor(Object, Span`1)
MethodBaseInvoker.InvokeWithOneArg(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)

[ajcvickers]

This issue is lacking enough information for us to be able to fully understand what is happening. Please attach a small, runnable project or post a small, runnable code listing that reproduces what you are seeing so that we can investigate.

[lucasdelsilva]

Bro, I had the same problem with versions, I was having this same error after the update, unfortunately version 9 is still in preview "Basically", so the most advisable thing is to go back to version 8.11 and continue until they fix this error...

In my case it was this...

Before with the Error (V9):

<PackageReference Include="Microsoft.EntityFrameworkCore" Version="9.0.0" />
<PackageReference Include="Pomelo.EntityFrameworkCore.MySql" Version="8.0.2" />

After without the error (V8.11):

<PackageReference Include="Microsoft.EntityFrameworkCore" Version="8.0.11" />
<PackageReference Include="Pomelo.EntityFrameworkCore.MySql" Version="8.0.2" />

[SimonCropp]

My assumption is that Pomelo.EntityFrameworkCore.MySql is using an internal API of EF, and needs to be updated to EF V9

Probs better to close this and add a comment this this thread PomeloFoundation/Pomelo.EntityFrameworkCore.MySql#1841

[rwb196884]

I do not use MySQL.