Target framework version of Microsoft.NETCore.App\2.1.30\mscorlib.dll returning .NETFramework,Version=v4.0

[e82eric]

Hi, when I try to get the target framework version of Microsoft.NETCore.App\2.1.30\mscorlib.dll it comes back as ".NETFramework,Version=v4.0". I have a feeling I am doing something wrong. Below is the test I was using.

It looked like it has to do with these 2 lines.

ILSpy/ICSharpCode.Decompiler/Metadata/DotNetCorePathFinderExtensions.cs

Line 65 in 397661b

return blobReader.ReadSerializedString()?.Replace(" ", "");

ILSpy/ICSharpCode.Decompiler/Metadata/DotNetCorePathFinderExtensions.cs

Line 80 in 397661b

return $".NETFramework,Version=v{assemblyDefinition.Version.ToString(2)}";

It looked like "2.1.30", "3.1.32" didn't have the TargetFrameworkAttribute and all of the newer did have that attribute. (All versions had mscorlib as the name for line 80).

using System.IO;
using System.Reflection.Metadata;
using System.Reflection.PortableExecutable;
using ICSharpCode.Decompiler;
using ICSharpCode.Decompiler.Metadata;

namespace TestNetCoreTwoTargetFrameworkResolution
{
    internal class Program
    {
        public static void Main(string[] args)
        {
            var versions = new string[] { "2.1.30", "3.1.32", "6.0.16", "7.0.5", "8.0.0-preview.3.23174.8" };
            foreach (var version in versions)
            {
                var assemblyPath = $@"C:\Program Files\dotnet\shared\Microsoft.NETCore.App\{version}\mscorlib.dll";
                // var assemblyPath = @"C:\Program Files\dotnet\shared\Microsoft.NETCore.App\7.0.5\mscorlib.dll";
                var options = MetadataReaderOptions.ApplyWindowsRuntimeProjections;

                using (var fileStream = new FileStream(assemblyPath, FileMode.Open, FileAccess.Read))
                {
                    var peFile = new PEFile(
                        assemblyPath,
                        fileStream,
                        PEStreamOptions.PrefetchEntireImage,
                        metadataOptions: options);

                    AssemblyDefinition assemblyDefinition = peFile.Metadata.GetAssemblyDefinition();
                    var frameworkId = GetTargetFrameworkId(peFile.Metadata);
                    var name = peFile.Metadata.GetString(assemblyDefinition.Name);
                    var targetFrameworkId = peFile.DetectTargetFrameworkId();
                    Console.WriteLine($"{frameworkId} {name} {targetFrameworkId}");
                }
            }
        }

        const string TargetFrameworkAttributeName = "System.Runtime.Versioning.TargetFrameworkAttribute";
        public static string GetTargetFrameworkId(MetadataReader metadata)
        {
            foreach (var h in metadata.GetCustomAttributes(Handle.AssemblyDefinition))
            {
                var attribute = metadata.GetCustomAttribute(h);
                if (attribute.GetAttributeType(metadata).GetFullTypeName(metadata).ToString() !=
                    TargetFrameworkAttributeName)
                    continue;
                var blobReader = metadata.GetBlobReader(attribute.Value);
                if (blobReader.ReadUInt16() == 0x0001)
                {
                    return blobReader.ReadSerializedString()?.Replace(" ", "");
                }
            }

            return null;
        }
    }
}```


Output:
 mscorlib .NETFramework,Version=v4.0
 mscorlib .NETFramework,Version=v4.0
.NETCoreApp,Version=v6.0 mscorlib .NETCoreApp,Version=v6.0
.NETCoreApp,Version=v7.0 mscorlib .NETCoreApp,Version=v7.0
.NETCoreApp,Version=v8.0 mscorlib .NETCoreApp,Version=v8.0