Fixed PluginAssemblyLoadContext so it won't reload already loaded assemblies. (#214)

The appveyor build did not succeed but I guess that's OK since I will continue to work on this branch.

src/Microsoft.IIS.Administration/Extensibility/ModuleLoader.cs

@@ -39,12 +39,17 @@ namespace Microsoft.IIS.Administration
             Log.Logger.Debug($"Loading plugin {assemblyName}");
 
             Assembly assembly = _loader.LoadFromAssemblyPath(assemblyPath);
+
             _loadedAssemblies.Add(assembly);
 
+            //
             // Every module should expose a type called Startup in a namespace equivalent to the assembly name
-            Type type = assembly.GetType(assemblyName + ".Startup"); 
-            IModule module = (IModule) Activator.CreateInstance(type);
+            Type type = assembly.GetType(assemblyName + ".Startup");
+
+            IModule module = (IModule)Activator.CreateInstance(type);
+
             _moduleHolder.Add(module);
+
             return assembly;
         }
 

src/Microsoft.IIS.Administration/Extensibility/PluginAssemblyLoadContext.cs

@@ -24,6 +24,12 @@ namespace Microsoft.IIS.Administration
 
         protected override Assembly Load(AssemblyName assemblyName)
         {
+            AssemblyName loaded = Assembly.GetEntryAssembly().GetReferencedAssemblies().FirstOrDefault(a => a.Name.Equals(assemblyName.Name));
+
+            if (loaded != null)
+            {
+                return Assembly.Load(loaded);
+            }
 
             Assembly asm = null;