Merge pull request #647 from Excel-DNA/2ALC

 Added AssemblyLoadContext dependent search for already loaded assembly in .NET 6

Author: govert

Source/ExcelDna.Integration/ExternalLibrary.cs

@@ -243,12 +243,24 @@ internal List<ExportedAssembly> GetAssemblies(string pathResolveRoot, DnaLibrary
         // But here we don't deal with .resources assemblies
         static Assembly GetAssemblyIfLoaded(string assemblyName)
         {
-            Assembly[] assemblies = AppDomain.CurrentDomain.GetAssemblies();
-            foreach (Assembly loadedAssembly in assemblies)
+            IEnumerable<Assembly> assemblies = null;
+#if NETCOREAPP
+            var alc = System.Runtime.Loader.AssemblyLoadContext.GetLoadContext(Assembly.GetExecutingAssembly());
+            if (alc != null)
             {
-                AssemblyName loadedAssemblyName = loadedAssembly.GetName();
-                if (string.Equals(assemblyName, loadedAssemblyName.Name, StringComparison.OrdinalIgnoreCase))
-                    return loadedAssembly;
+                assemblies = alc.Assemblies;
+            }
+#else
+            assemblies = AppDomain.CurrentDomain.GetAssemblies();
+#endif
+            if (assemblies != null)
+            {
+                foreach (Assembly loadedAssembly in assemblies)
+                {
+                    AssemblyName loadedAssemblyName = loadedAssembly.GetName();
+                    if (string.Equals(assemblyName, loadedAssemblyName.Name, StringComparison.OrdinalIgnoreCase))
+                        return loadedAssembly;
+                }
             }
             return null;
         }

Source/ExcelDna.Integration/Logging.cs

@@ -197,6 +197,8 @@ static void Close()
                 IntegrationTraceSource.Close();
                 IntegrationTraceSource = null;
             }
+
+            s_LoggingInitialized = false;
         }
 
     }

Source/ExcelDna.ManagedHost/AddInInitialize.cs

@@ -67,6 +67,9 @@ private static void UnloadALC()
                 GC.Collect();
                 GC.WaitForPendingFinalizers();
             }
+
+            if (alcWeakRef.IsAlive)
+                Logger.Initialization.Warn("Failed to unload AssemblyLoadContext");
         }
 
         private static WeakReference StartUnloadALC()