ArgumentNullException in beta.6

[timcassell]

AsmResolver Version

6.0.0.beta.6

.NET Version

No response

Operating System

Windows

Describe the Bug

When running in Visual Studio, ModuleDefinition.FromFile throws ArgumentNullException. It does not happen when running dotnet build on command line. The exception did not happen in either environment in beta.5.

How To Reproduce

Create an MSBuild task that runs during the build that calls ModuleDefinition.FromFile, run it in Visual Studio 2026. For an already existing repro, you can pull dotnet/BenchmarkDotNet@a0a31a0 and build it in VS.

Expected Behavior

No exception

Actual Behavior

System.ArgumentNullException: Value cannot be null.
Parameter name: v1
   at System.Version.op_LessThan(Version v1, Version v2)
   at AsmResolver.DotNet.TargetRuntimeProber.TraverseAssemblyReferences(MetadataStreamSelection& streams, DotNetRuntimeInfo& dotNetRuntimeInfo)
   at AsmResolver.DotNet.TargetRuntimeProber.TryGetLikelyTargetRuntime(MetadataStreamSelection& streams, DotNetRuntimeInfo& targetRuntime)
   at AsmResolver.DotNet.TargetRuntimeProber.TryGetLikelyTargetRuntime(PEImage image, DotNetRuntimeInfo& targetRuntime)
   at AsmResolver.DotNet.Serialized.SerializedModuleDefinition..ctor(PEImage peImage, ModuleReaderParameters readerParameters)
   at AsmResolver.DotNet.ModuleDefinition.FromImage(PEImage image, ModuleReaderParameters readerParameters, Boolean createRuntimeContext)
   at BenchmarkDotNet.Weaver.WeaveAssemblyTask.Execute()

Additional Context

No response

[Washi1337]

Fun.

I assume Visual Studio runs under .NET FX and dotnet build on .NET (Core), because this seems to be a direct result of the differences in implementations between the two in operator < (Version, Version) that I didn't take into account when introducing TargetRuntimeProber.

• .NET FX checks for null and throws: https://github.com/microsoft/referencesource/blob/ec9fa9ae770d522a5b5f0607898044b7478574a3/mscorlib/system/version.cs#L450-L455

• .NET (Core) checks for null but does not throw: https://github.com/dotnet/runtime/blob/40f1da5b33c54b0fb8d76bca08f88c9874c57061/src/libraries/System.Private.CoreLib/src/System/Version.cs#L481-L489

Side note, we may want to consider running unit tests on .NET FX too in CI/CD.

[Washi1337]

Nightly will shortly feature a fix for this. I will likely hotpatch this together with a few other regressions that were found. Until then, could you verify if this indeed fixes the problem?

[timcassell]

Yep, development.403 fixed it.

[Washi1337]

Should be on nuget now as 6.0.0-rc.1.

Thanks again for reporting.