Look for TargetFrameworkAttribute for CoreRuntime.

Author: timcassell

src/BenchmarkDotNet/Environments/Runtimes/CoreRuntime.cs

@@ -46,6 +46,12 @@ public static CoreRuntime CreateForNewVersion(string msBuildMoniker, string disp
             return new CoreRuntime(RuntimeMoniker.NotRecognized, msBuildMoniker, displayName);
         }
 
+        internal static CoreRuntime GetTargetOrCurrentVersion(Assembly? assembly)
+            // Try to determine the Framework version that the assembly was compiled for.
+            => GetTargetFrameworkVersion(assembly)
+                // Fallback to the current running Framework version.
+                ?? GetCurrentVersion();
+
         internal static CoreRuntime GetCurrentVersion()
         {
             if (!RuntimeInformation.IsNetCore)
@@ -243,5 +249,32 @@ private static CoreRuntime GetPlatformSpecific(CoreRuntime fallback)
 
             return new CoreRuntime(fallback.RuntimeMoniker, $"{fallback.MsBuildMoniker}-{platformName}", fallback.Name);
         }
+
+        private static CoreRuntime? GetTargetFrameworkVersion(Assembly? assembly)
+        {
+            if (assembly is null)
+            {
+                return null;
+            }
+
+            // Look for a TargetFrameworkAttribute with a supported Framework version.
+            foreach (var attribute in assembly.GetCustomAttributes<TargetFrameworkAttribute>())
+            {
+                //.NETCoreApp,Version=vX.Y
+                const string FrameworkPrefix = ".NETCoreApp,Version=v";
+                var framework = attribute.FrameworkName;
+                if (framework?.StartsWith(FrameworkPrefix) == true
+                    && Version.TryParse(framework[FrameworkPrefix.Length..], out var version)
+                    // We don't support netcoreapp1.X
+                    && version.Major >= 2)
+                {
+                    return FromVersion(version);
+                }
+            }
+
+            // TargetFrameworkAttribute not found, or the assembly targeted a version older than we support,
+            // or the assembly targeted a non-core framework (like netstandard2.0).
+            return null;
+        }
     }
 }

src/BenchmarkDotNet/Portability/RuntimeInformation.cs

@@ -171,9 +171,18 @@ string GetDetailedVersion()
         }
 
         internal static Runtime GetTargetOrCurrentRuntime(Assembly? assembly)
-            => !IsMono && !IsWasm && IsFullFramework // Match order of checks in GetCurrentRuntime().
-                ? ClrRuntime.GetTargetOrCurrentVersion(assembly)
-                : GetCurrentRuntime();
+        {
+            // Match order of checks in GetCurrentRuntime().
+            if (!IsMono && !IsWasm)
+            {
+                if (IsFullFramework)
+                    return ClrRuntime.GetTargetOrCurrentVersion(assembly);
+                // 99% of the time the core runtime is the same as the target framework, but the runtime could roll forward if it's not self-contained.
+                if (IsNetCore)
+                    return CoreRuntime.GetTargetOrCurrentVersion(assembly);
+            }
+            return GetCurrentRuntime();
+        }
 
         internal static Runtime GetCurrentRuntime()
         {