Could not find core Assembly in MetadataLoadContext

[msedi]

Description

I was switching to the preview of .NET 8 to try out the behavior of the framework.
Everything worked before so that switch to .NET 8 causes the problem. The code is simply Following:

            PathAssemblyResolver resolver = new(SearchFileNames);
            var ctx = new MetadataLoadContext(resolver);

has something changed here?

Thanks

Reproduction Steps

I'm not sure if this is a known problem, and the core assembly needs to be handed over now.

Expected behavior

Core assembly should not be needed.

Actual behavior

It simply works.

Regression?

Yes, in .NET7 it worked, now in .NET8 it doesn't work anymore.

Known Workarounds

Switch back to .NET7

Configuration

.NET8 / win-x64
Windows 10

Other information

No response

Tagging subscribers to this area: @dotnet/area-system-reflection
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Description

I was switching to the preview of .NET 8 to try out the behavior of the framework.
Everything worked before so that switch to .NET 8 causes the problem. The code is simply Following:

            PathAssemblyResolver resolver = new(SearchFileNames);
            var ctx = new MetadataLoadContext(resolver);

has something changed here?

Thanks

Reproduction Steps

I'm not sure if this is a known problem, and the core assembly needs to be handed over now.

Expected behavior

Core assembly should not be needed.

Actual behavior

It simply works.

Regression?

Yes, in .NET7 it worked, now in .NET8 it doesn't work anymore.

Known Workarounds

Switch back to .NET7

Configuration

.NET8 / win-x64
Windows 10

Other information

No response

Author:	msedi
Assignees:	-
Labels:	area-System.Reflection, untriaged
Milestone:	-

[msedi]

It seems it has been reported already before: #41921
The questions still is why did it work on .NET7?

[steveharter]

No changes to my knowledge were made from v7 to v8 to MetadataLoadContext that would have affected the loading behavior of the core assembly.

I assume the example in #41921 (comment) works?

This issue has been marked needs-author-action and may be missing some important information.

[msedi]

@steveharter: Sorry for the delay, I wasn't recognizing your reply. No, the example doesn't work. As described above the original code

in .NET7

            PathAssemblyResolver resolver = new(new List<string>(SearchFileNames));
            var ctx = new MetadataLoadContext(resolver);

I get this:

System.IO.FileNotFoundException: 'Could not find core assembly. Either specify a valid core assembly name in the MetadataLoadContext constructor or provide a MetadataAssemblyResolver that can load the core assembly.'

in NET8:

            // For some reasons the coreLib has to be given
            // see: https://github.com/dotnet/runtime/issues/41921
            Assembly coreAssembly = typeof(object).Assembly;

            PathAssemblyResolver resolver = new(new List<string>(SearchFileNames) { coreAssembly.Location });
            var ctx = new MetadataLoadContext(resolver, coreAssembly.GetName().Name);

I get this:

System.IO.FileNotFoundException: 'Could not find assembly 'System.Runtime, Version=8.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. Either explicitly load this assembly using a method such as LoadFromAssemblyPath() or use a MetadataAssemblyResolver that returns a valid assembly.'

when accessing CustomAttributeData.AttributeType.