1 files changed, 37 insertions, 21 deletions

diff --git a/src/binder/clrprivbinderassemblyloadcontext.cpp b/src/binder/clrprivbinderassemblyloadcontext.cpp
index 8f3a3eef49..57f4ee72c4 100644
--- a/src/binder/clrprivbinderassemblyloadcontext.cpp
+++ b/src/binder/clrprivbinderassemblyloadcontext.cpp
@@ -61,19 +61,14 @@ HRESULT CLRPrivBinderAssemblyLoadContext::BindAssemblyByName(IAssemblyName     *
         SAFE_NEW(pAssemblyName, AssemblyName);
         IF_FAIL_GO(pAssemblyName->Init(pIAssemblyName));
         
-        // When LoadContext needs to resolve an assembly reference, it will go through the following lookup order:
-        //
-        // 1) Lookup the assembly within the LoadContext itself. If assembly is found, use it.
-        // 2) Invoke the LoadContext's Load method implementation. If assembly is found, use it.
-        // 3) Lookup the assembly within TPABinder. If assembly is found, use it.
-        // 4) Invoke the LoadContext's Resolving event. If assembly is found, use it.
-        // 5) Raise exception.
-        //
-        // This approach enables a LoadContext to override assemblies that have been loaded in TPA context by loading
-        // a different (or even the same!) version.
-        
+        // Check if the assembly is in the TPA list or not. Don't search app paths when using the TPA binder because the actual
+        // binder is using a host assembly resolver.
+        hr = m_pTPABinder->BindAssemblyByNameWorker(pAssemblyName, &pCoreCLRFoundAssembly, true /* excludeAppPaths */);
+        if (hr == HRESULT_FROM_WIN32(ERROR_FILE_NOT_FOUND))
         {
-            // Step 1 - Try to find the assembly within the LoadContext.
+            // If we could not find the assembly in the TPA list,
+            // then bind to it in the context of the current binder.
+            // If we find it already loaded, we will return the reference.
             hr = BindAssemblyByNameWorker(pAssemblyName, &pCoreCLRFoundAssembly);
             if ((hr == HRESULT_FROM_WIN32(ERROR_FILE_NOT_FOUND)) ||
                 (hr == FUSION_E_APP_DOMAIN_LOCKED) || (hr == FUSION_E_REF_DEF_MISMATCH))
@@ -87,8 +82,7 @@ HRESULT CLRPrivBinderAssemblyLoadContext::BindAssemblyByName(IAssemblyName     *
                 // Thus, if default binder has been overridden, then invoke it in an attempt to perform the binding for it make the call
                 // of what to do next. The host-overridden binder can either fail the bind or return reference to an existing assembly
                 // that has been loaded.
-                //
-                hr = AssemblyBinder::BindUsingHostAssemblyResolver(GetManagedAssemblyLoadContext(), pAssemblyName, pIAssemblyName, m_pTPABinder, &pCoreCLRFoundAssembly);
+                hr = AssemblyBinder::BindUsingHostAssemblyResolver(GetManagedAssemblyLoadContext(), pAssemblyName, pIAssemblyName, &pCoreCLRFoundAssembly);
                 if (SUCCEEDED(hr))
                 {
                     // We maybe returned an assembly that was bound to a different AssemblyLoadContext instance.
@@ -148,19 +142,41 @@ HRESULT CLRPrivBinderAssemblyLoadContext::BindUsingPEImage( /* in */ PEImage *pP
             IF_FAIL_GO(HRESULT_FROM_WIN32(ERROR_BAD_FORMAT));
         }
         
-        // Disallow attempt to bind to the core library. Aside from that,
-        // the LoadContext can load any assembly (even if it was in a different LoadContext like TPA).
+        // Ensure we are not being asked to bind to a TPA assembly
+        //
+        // Easy out for mscorlib
         if (pAssemblyName->IsMscorlib())
         {
             IF_FAIL_GO(HRESULT_FROM_WIN32(ERROR_FILE_NOT_FOUND));
         }
 
-        hr = AssemblyBinder::BindUsingPEImage(&m_appContext, pAssemblyName, pPEImage, PeKind, pIMetaDataAssemblyImport, &pCoreCLRFoundAssembly);
-        if (hr == S_OK)
         {
-            _ASSERTE(pCoreCLRFoundAssembly != NULL);
-            pCoreCLRFoundAssembly->SetBinder(this);
-            *ppAssembly = pCoreCLRFoundAssembly.Extract();
+            SString& simpleName = pAssemblyName->GetSimpleName();
+            ApplicationContext *pTPAApplicationContext = m_pTPABinder->GetAppContext();
+            SimpleNameToFileNameMap * tpaMap = pTPAApplicationContext->GetTpaList();
+            if (tpaMap->LookupPtr(simpleName.GetUnicode()) != NULL)
+            {
+                // The simple name of the assembly being requested to be bound was found in the TPA list.
+                // Now, perform the actual bind to see if the assembly was really in the TPA assembly or not.
+                // Don't search app paths when using the TPA binder because the actual binder is using a host assembly resolver.
+                hr = m_pTPABinder->BindAssemblyByNameWorker(pAssemblyName, &pCoreCLRFoundAssembly, true /* excludeAppPaths */);
+                if (SUCCEEDED(hr))
+                {
+                    if (pCoreCLRFoundAssembly->GetIsInGAC())
+                    {
+                        // If we were able to bind to a TPA assembly, then fail the load
+                        IF_FAIL_GO(HRESULT_FROM_WIN32(ERROR_FILE_NOT_FOUND));
+                    }
+                }
+            }
+            
+            hr = AssemblyBinder::BindUsingPEImage(&m_appContext, pAssemblyName, pPEImage, PeKind, pIMetaDataAssemblyImport, &pCoreCLRFoundAssembly);
+            if (hr == S_OK)
+            {
+                _ASSERTE(pCoreCLRFoundAssembly != NULL);
+                pCoreCLRFoundAssembly->SetBinder(this);
+                *ppAssembly = pCoreCLRFoundAssembly.Extract();
+            }
         }
 Exit:;        
     }