Merge pull request #19970 from CyrusNajmabadi/addUsingOOP6

Extract a service component from Add-using independent of the CodeFixProvider

src/EditorFeatures/Core/Implementation/CodeFixes/CodeFixService.cs

@@ -465,24 +465,8 @@ private async Task<IEnumerable<Diagnostic>> GetProjectDiagnosticsAsync(Project p
         private bool IsInteractiveCodeFixProvider(CodeFixProvider provider)
         {
             // TODO (https://github.com/dotnet/roslyn/issues/4932): Don't restrict CodeFixes in Interactive
-            if (provider is FullyQualify.AbstractFullyQualifyCodeFixProvider)
-            {
-                return true;
-            }
-
-            var providerType = provider?.GetType();
-            while (providerType != null)
-            {
-                if (providerType.IsConstructedGenericType &&
-                    providerType.GetGenericTypeDefinition() == typeof(AddImport.AbstractAddImportCodeFixProvider<>))
-                {
-                    return true;
-                }
-
-                providerType = providerType.GetTypeInfo().BaseType;
-            }
-
-            return false;
+            return provider is FullyQualify.AbstractFullyQualifyCodeFixProvider ||
+                   provider is AddImport.AbstractAddImportCodeFixProvider;
         }
 
         private static readonly Func<DiagnosticId, List<CodeFixProvider>> s_createList = _ => new List<CodeFixProvider>();

src/Features/CSharp/Portable/AddImport/CSharpAddImportCodeFixProvider.cs

@@ -14,6 +14,7 @@
 using Microsoft.CodeAnalysis.CSharp.Symbols;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Formatting;
+using Microsoft.CodeAnalysis.Host.Mef;
 using Microsoft.CodeAnalysis.LanguageServices;
 using Microsoft.CodeAnalysis.Packaging;
 using Microsoft.CodeAnalysis.Shared.Extensions;
@@ -147,7 +148,7 @@ internal static class AddImportDiagnosticIds
     }
 
     [ExportCodeFixProvider(LanguageNames.CSharp, Name = PredefinedCodeFixProviderNames.AddImport), Shared]
-    internal class CSharpAddImportCodeFixProvider : AbstractAddImportCodeFixProvider<SimpleNameSyntax>
+    internal class CSharpAddImportCodeFixProvider : AbstractAddImportCodeFixProvider
     {
         public override ImmutableArray<string> FixableDiagnosticIds => AddImportDiagnosticIds.FixableDiagnosticIds;
 
@@ -162,7 +163,11 @@ public CSharpAddImportCodeFixProvider()
             : base(installerService, symbolSearchService)
         {
         }
+    }
 
+    [ExportLanguageService(typeof(IAddImportFeatureService), LanguageNames.CSharp), Shared]
+    internal class CSharpAddImportFeatureService : AbstractAddImportFeatureService<SimpleNameSyntax>
+    {
         protected override bool CanAddImport(SyntaxNode node, CancellationToken cancellationToken)
         {
             if (cancellationToken.IsCancellationRequested)

src/Features/Core/Portable/AddImport/AbstractAddImportCodeFixProvider.cs

@@ -13,17 +13,15 @@
 using Microsoft.CodeAnalysis.Host;
 using Microsoft.CodeAnalysis.Internal.Log;
 using Microsoft.CodeAnalysis.LanguageServices;
-using Microsoft.CodeAnalysis.Options;
 using Microsoft.CodeAnalysis.Packaging;
 using Microsoft.CodeAnalysis.Shared.Extensions;
 using Microsoft.CodeAnalysis.SymbolSearch;
+using Microsoft.CodeAnalysis.Text;
 using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.AddImport
 {
-    internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSyntax> 
-        : CodeFixProvider, IEqualityComparer<PortableExecutableReference>
-        where TSimpleNameSyntax : SyntaxNode
+    internal abstract partial class AbstractAddImportCodeFixProvider : CodeFixProvider
     {
         private const int MaxResults = 3;
 
@@ -41,6 +39,111 @@ internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSynt
             _symbolSearchService = symbolSearchService;
         }
 
+        public sealed override async Task RegisterCodeFixesAsync(CodeFixContext context)
+        {
+            var document = context.Document;
+            var span = context.Span;
+            var cancellationToken = context.CancellationToken;
+
+            var addImportService = document.GetLanguageService<IAddImportFeatureService>();
+
+            var solution = document.Project.Solution;
+            var options = solution.Options;
+
+            var searchReferenceAssemblies = options.GetOption(SymbolSearchOptions.SuggestForTypesInReferenceAssemblies, document.Project.Language);
+            var searchNuGetPackages = options.GetOption(SymbolSearchOptions.SuggestForTypesInNuGetPackages, document.Project.Language);
+
+            var symbolSearchService = searchReferenceAssemblies || searchNuGetPackages
+                ? _symbolSearchService ?? solution.Workspace.Services.GetService<ISymbolSearchService>()
+                : null;
+
+            var packageSources = symbolSearchService != null && searchNuGetPackages
+                ? GetPackageSources(document)
+                : ImmutableArray<PackageSource>.Empty;
+
+            // We might have multiple different diagnostics covering the same span.  Have to
+            // process them all as we might produce different fixes for each diagnostic.
+
+            foreach (var diagnostic in context.Diagnostics)
+            {
+                var fixes = await addImportService.GetFixesAsync(
+                    document, span, diagnostic.Id, symbolSearchService,
+                    searchReferenceAssemblies, packageSources,
+                    cancellationToken).ConfigureAwait(false);
+
+                var codeActions = ArrayBuilder<CodeAction>.GetInstance();
+
+                foreach (var fix in fixes)
+                {
+                    var codeAction = TryCreateCodeAction(document, fix);
+                    codeActions.AddIfNotNull(codeAction);
+
+                    if (codeActions.Count >= MaxResults)
+                    {
+                        break;
+                    }
+                }
+
+                context.RegisterFixes(codeActions, diagnostic);
+                codeActions.Free();
+            }
+        }
+
+        private IPackageInstallerService GetPackageInstallerService(Document document)
+            => _packageInstallerService ?? document.Project.Solution.Workspace.Services.GetService<IPackageInstallerService>();
+
+        private ImmutableArray<PackageSource> GetPackageSources(Document document)
+            => GetPackageInstallerService(document)?.PackageSources ?? ImmutableArray<PackageSource>.Empty;
+
+        private CodeAction TryCreateCodeAction(Document document, AddImportFixData fixData)
+        {
+            if (fixData == null)
+            {
+                return null;
+            }
+
+            switch (fixData.Kind)
+            {
+                case AddImportFixKind.ProjectSymbol:
+                    return new ProjectSymbolReferenceCodeAction(document, fixData);
+
+                case AddImportFixKind.MetadataSymbol:
+                    return new MetadataSymbolReferenceCodeAction(document, fixData);
+
+                case AddImportFixKind.ReferenceAssemblySymbol:
+                    return new AssemblyReferenceCodeAction(document, fixData);
+
+                case AddImportFixKind.PackageSymbol:
+                    var packageInstaller = GetPackageInstallerService(document);
+                    return !packageInstaller.IsInstalled(document.Project.Solution.Workspace, document.Project.Id, fixData.PackageName)
+                        ? new ParentInstallPackageCodeAction(document, fixData, GetPackageInstallerService(document))
+                        : null;
+            }
+
+            throw ExceptionUtilities.Unreachable;
+        }
+    }
+
+    internal interface IAddImportFeatureService : ILanguageService
+    {
+        Task<ImmutableArray<AddImportFixData>> GetFixesAsync(
+            Document document, TextSpan span, string diagnosticId, ISymbolSearchService symbolSearchService,
+            bool searchReferenceAssemblies, ImmutableArray<PackageSource> packageSources, CancellationToken cancellationToken);
+    }
+
+    internal abstract partial class AbstractAddImportFeatureService<TSimpleNameSyntax> 
+        : IAddImportFeatureService, IEqualityComparer<PortableExecutableReference>
+        where TSimpleNameSyntax : SyntaxNode
+    {
+        private const int MaxResults = 3;
+
+        /// <summary>
+        /// Values for these parameters can be provided (during testing) for mocking purposes.
+        /// </summary> 
+        protected AbstractAddImportFeatureService()
+        {
+        }
+
         protected abstract bool CanAddImport(SyntaxNode node, CancellationToken cancellationToken);
         protected abstract bool CanAddImportForMethod(string diagnosticId, ISyntaxFactsService syntaxFacts, SyntaxNode node, out TSimpleNameSyntax nameNode);
         protected abstract bool CanAddImportForNamespace(string diagnosticId, SyntaxNode node, out TSimpleNameSyntax nameNode);
@@ -61,35 +164,16 @@ internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSynt
         protected abstract string GetDescription(IReadOnlyList<string> nameParts);
         protected abstract (string description, bool hasExistingImport) GetDescription(Document document, INamespaceOrTypeSymbol symbol, SemanticModel semanticModel, SyntaxNode root, CancellationToken cancellationToken);
 
-        public sealed override async Task RegisterCodeFixesAsync(CodeFixContext context)
-        {
-            // We might have multiple different diagnostics covering the same span.  Have to
-            // process them all as we might produce different fixes for each diagnostic.
-            var resultCount = 0;
-            foreach (var diagnostic in context.Diagnostics)
-            {
-                var codeActions = await GetCodeActionsAsync(context, diagnostic).ConfigureAwait(false);
-                context.RegisterFixes(codeActions, diagnostic);
-
-                resultCount += codeActions.Length;
-                if (resultCount >= MaxResults)
-                {
-                    break;
-                }
-            }
-        }
-
-        private async Task<ImmutableArray<CodeAction>> GetCodeActionsAsync(CodeFixContext context, Diagnostic diagnostic)
+        public async Task<ImmutableArray<AddImportFixData>> GetFixesAsync(
+            Document document, TextSpan span, string diagnosticId, ISymbolSearchService symbolSearchService,
+            bool searchReferenceAssemblies, ImmutableArray<PackageSource> packageSources,
+            CancellationToken cancellationToken)
         {
-            var document = context.Document;
-            var span = context.Span;
-            var cancellationToken = context.CancellationToken;
-
             var root = await document.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
             var node = root.FindToken(span.Start, findInsideTrivia: true)
                            .GetAncestor(n => n.Span.Contains(span) && n != root);
 
-            var result = ArrayBuilder<CodeAction>.GetInstance();
+            var result = ArrayBuilder<AddImportFixData>.GetInstance();
             if (node != null)
             {
                 var documentOptions = await document.GetOptionsAsync(cancellationToken).ConfigureAwait(false);
@@ -103,7 +187,9 @@ private async Task<ImmutableArray<CodeAction>> GetCodeActionsAsync(CodeFixContex
                         if (this.CanAddImport(node, cancellationToken))
                         {
                             var semanticModel = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
-                            var allSymbolReferences = await FindResultsAsync(document, semanticModel, diagnostic.Id, node, cancellationToken).ConfigureAwait(false);
+                            var allSymbolReferences = await FindResultsAsync(
+                                document, semanticModel, diagnosticId, node, symbolSearchService, 
+                                searchReferenceAssemblies, packageSources, cancellationToken).ConfigureAwait(false);
 
                             // Nothing found at all. No need to proceed.
                             foreach (var reference in allSymbolReferences)
@@ -111,9 +197,7 @@ private async Task<ImmutableArray<CodeAction>> GetCodeActionsAsync(CodeFixContex
                                 cancellationToken.ThrowIfCancellationRequested();
 
                                 var fixData = await reference.TryGetFixDataAsync(document, node, placeSystemNamespaceFirst, cancellationToken).ConfigureAwait(false);
-                                var codeAction = TryCreateCodeAction(document, fixData);
-
-                                result.AddIfNotNull(codeAction);
+                                result.AddIfNotNull(fixData);
                             }
                         }
                     }
@@ -123,36 +207,9 @@ private async Task<ImmutableArray<CodeAction>> GetCodeActionsAsync(CodeFixContex
             return result.ToImmutableAndFree();
         }
 
-        private CodeAction TryCreateCodeAction(Document document, AddImportFixData fixData)
-        {
-            if (fixData == null)
-            {
-                return null;
-            }
-
-            switch (fixData.Kind)
-            {
-                case AddImportFixKind.ProjectSymbol:
-                    return new ProjectSymbolReferenceCodeAction(document, fixData);
-
-                case AddImportFixKind.MetadataSymbol:
-                    return new MetadataSymbolReferenceCodeAction(document, fixData);
-
-                case AddImportFixKind.ReferenceAssemblySymbol:
-                    return new AssemblyReferenceCodeAction(document, fixData);
-
-                case AddImportFixKind.PackageSymbol:
-                    var packageInstaller = GetPackageInstallerService(document);
-                    return !packageInstaller.IsInstalled(document.Project.Solution.Workspace, document.Project.Id, fixData.PackageName)
-                        ? new ParentInstallPackageCodeAction(document, fixData, GetPackageInstallerService(document))
-                        : null;
-            }
-
-            throw ExceptionUtilities.Unreachable;
-        }
-
         private async Task<ImmutableArray<Reference>> FindResultsAsync(
-            Document document, SemanticModel semanticModel, string diagnosticId, SyntaxNode node, CancellationToken cancellationToken)
+            Document document, SemanticModel semanticModel, string diagnosticId, SyntaxNode node, ISymbolSearchService symbolSearchService, 
+            bool searchReferenceAssemblies, ImmutableArray<PackageSource> packageSources, CancellationToken cancellationToken)
         {
             // Caches so we don't produce the same data multiple times while searching 
             // all over the solution.
@@ -160,15 +217,9 @@ private CodeAction TryCreateCodeAction(Document document, AddImportFixData fixDa
             var projectToAssembly = new ConcurrentDictionary<Project, AsyncLazy<IAssemblySymbol>>(concurrencyLevel: 2, capacity: project.Solution.ProjectIds.Count);
             var referenceToCompilation = new ConcurrentDictionary<PortableExecutableReference, Compilation>(concurrencyLevel: 2, capacity: project.Solution.Projects.Sum(p => p.MetadataReferences.Count));
 
-            var language = document.Project.Language;
-            var options = document.Project.Solution.Options;
-
-            var symbolSearchService = GetSymbolSearchService(document);
-            var packageSources = GetPackageSources(document, symbolSearchService);
-
             var finder = new SymbolReferenceFinder(
-                this, document, semanticModel, diagnosticId, node,
-                symbolSearchService, packageSources, cancellationToken);
+                this, document, semanticModel, diagnosticId, node, symbolSearchService,
+                searchReferenceAssemblies, packageSources, cancellationToken);
 
             // Look for exact matches first:
             var exactReferences = await FindResultsAsync(projectToAssembly, referenceToCompilation, project, finder, exact: true, cancellationToken: cancellationToken).ConfigureAwait(false);
@@ -191,30 +242,6 @@ private CodeAction TryCreateCodeAction(Document document, AddImportFixData fixDa
             return fuzzyReferences;
         }
 
-        private ISymbolSearchService GetSymbolSearchService(Document document) 
-            => document.Project.Solution.Options.GetOption(SymbolSearchOptions.SuggestForTypesInReferenceAssemblies, document.Project.Language)
-                ? _symbolSearchService ?? document.Project.Solution.Workspace.Services.GetService<ISymbolSearchService>()
-                : null;
-
-        private IPackageInstallerService GetPackageInstallerService(Document document)
-            => document.Project.Solution.Options.GetOption(SymbolSearchOptions.SuggestForTypesInNuGetPackages, document.Project.Language)
-                ? _packageInstallerService ?? document.Project.Solution.Workspace.Services.GetService<IPackageInstallerService>()
-                : null;
-
-        private ImmutableArray<PackageSource> GetPackageSources(Document document, ISymbolSearchService searchService)
-        {
-            if (searchService != null)
-            {
-                var installerService = GetPackageInstallerService(document);
-                if (installerService?.IsEnabled(document.Project.Id) == true)
-                {
-                    return installerService.PackageSources;
-                }
-            }
-
-            return ImmutableArray<PackageSource>.Empty;
-        }
-
         private static bool IsHostOrTestWorkspace(Project project)
         {
             return project.Solution.Workspace.Kind == WorkspaceKind.Host ||

src/Features/Core/Portable/AddImport/CodeActions/AddImportCodeAction.cs

@@ -8,7 +8,7 @@
 
 namespace Microsoft.CodeAnalysis.AddImport
 {
-    internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSyntax>
+    internal abstract partial class AbstractAddImportCodeFixProvider
     {
         /// <summary>
         /// Code action we use when just adding a using, possibly with a project or

src/Features/Core/Portable/AddImport/CodeActions/AssemblyReferenceCodeAction.cs

@@ -10,7 +10,7 @@
 
 namespace Microsoft.CodeAnalysis.AddImport
 {
-    internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSyntax>
+    internal abstract partial class AbstractAddImportCodeFixProvider
     {
             private class AssemblyReferenceCodeAction : AddImportCodeAction
             {

src/Features/Core/Portable/AddImport/CodeActions/InstallPackageAndAddImportCodeAction.cs

@@ -12,7 +12,7 @@
 
 namespace Microsoft.CodeAnalysis.AddImport
 {
-    internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSyntax>
+    internal abstract partial class AbstractAddImportCodeFixProvider
     {
             private class InstallPackageAndAddImportCodeAction : AddImportCodeAction
             {

src/Features/Core/Portable/AddImport/CodeActions/InstallWithPackageManagerCodeAction.cs

@@ -9,7 +9,7 @@
 
 namespace Microsoft.CodeAnalysis.AddImport
 {
-    internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSyntax>
+    internal abstract partial class AbstractAddImportCodeFixProvider
     {
             private class InstallWithPackageManagerCodeAction : CodeAction
             {

src/Features/Core/Portable/AddImport/CodeActions/MetadataSymbolReferenceCodeAction.cs

@@ -5,7 +5,7 @@
 
 namespace Microsoft.CodeAnalysis.AddImport
 {
-    internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSyntax>
+    internal abstract partial class AbstractAddImportCodeFixProvider
     {
         private class MetadataSymbolReferenceCodeAction : SymbolReferenceCodeAction
         {

src/Features/Core/Portable/AddImport/CodeActions/ParentInstallPackageCodeAction.cs

@@ -10,7 +10,7 @@
 
 namespace Microsoft.CodeAnalysis.AddImport
 {
-    internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSyntax>
+    internal abstract partial class AbstractAddImportCodeFixProvider
     {
             /// <summary>
             /// This is the top level 'Install Nuget Package' code action we show in 

src/Features/Core/Portable/AddImport/CodeActions/ProjectSymbolReferenceCodeAction.cs

@@ -4,7 +4,7 @@
 
 namespace Microsoft.CodeAnalysis.AddImport
 {
-    internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSyntax>
+    internal abstract partial class AbstractAddImportCodeFixProvider
     {
         /// <summary>
         /// Code action for adding an import when we find a symbol in source in either our

src/Features/Core/Portable/AddImport/CodeActions/SymbolReference.SymbolReferenceCodeAction.cs

@@ -5,7 +5,7 @@
 
 namespace Microsoft.CodeAnalysis.AddImport
 {
-    internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSyntax>
+    internal abstract partial class AbstractAddImportCodeFixProvider
     {
             /// <summary>
             /// Code action we use when just adding a using, possibly with a project or

src/Features/Core/Portable/AddImport/References/AssemblyReference.cs

@@ -7,14 +7,14 @@
 
 namespace Microsoft.CodeAnalysis.AddImport
 {
-    internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSyntax>
+    internal abstract partial class AbstractAddImportFeatureService<TSimpleNameSyntax>
     {
         private partial class AssemblyReference : Reference
         {
             private readonly ReferenceAssemblyWithTypeResult _referenceAssemblyWithType;
 
             public AssemblyReference(
-                AbstractAddImportCodeFixProvider<TSimpleNameSyntax> provider,
+                AbstractAddImportFeatureService<TSimpleNameSyntax> provider,
                 SearchResult searchResult,
                 ReferenceAssemblyWithTypeResult referenceAssemblyWithType)
                 : base(provider, searchResult)

src/Features/Core/Portable/AddImport/References/MetadataSymbolReference.cs

@@ -11,7 +11,7 @@
 
 namespace Microsoft.CodeAnalysis.AddImport
 {
-    internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSyntax>
+    internal abstract partial class AbstractAddImportFeatureService<TSimpleNameSyntax>
     {
         private partial class MetadataSymbolReference : SymbolReference
         {
@@ -19,7 +19,7 @@ private partial class MetadataSymbolReference : SymbolReference
             private readonly PortableExecutableReference _reference;
 
             public MetadataSymbolReference(
-                AbstractAddImportCodeFixProvider<TSimpleNameSyntax> provider,
+                AbstractAddImportFeatureService<TSimpleNameSyntax> provider,
                 SymbolResult<INamespaceOrTypeSymbol> symbolResult,
                 ProjectId referenceProjectId,
                 PortableExecutableReference reference)

src/Features/Core/Portable/AddImport/References/PackageReference.cs

@@ -6,7 +6,7 @@
 
 namespace Microsoft.CodeAnalysis.AddImport
 {
-    internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSyntax>
+    internal abstract partial class AbstractAddImportFeatureService<TSimpleNameSyntax>
     {
         private partial class PackageReference : Reference
         {
@@ -15,7 +15,7 @@ private partial class PackageReference : Reference
             private readonly string _versionOpt;
 
             public PackageReference(
-                AbstractAddImportCodeFixProvider<TSimpleNameSyntax> provider,
+                AbstractAddImportFeatureService<TSimpleNameSyntax> provider,
                 SearchResult searchResult,
                 string source,
                 string packageName,

src/Features/Core/Portable/AddImport/References/ProjectSymbolReference.cs

@@ -9,7 +9,7 @@
 
 namespace Microsoft.CodeAnalysis.AddImport
 {
-    internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSyntax>
+    internal abstract partial class AbstractAddImportFeatureService<TSimpleNameSyntax>
     {
         /// <summary>
         /// Handles references to source symbols both from the current project the user is invoking
@@ -24,7 +24,7 @@ private partial class ProjectSymbolReference : SymbolReference
             private readonly Project _project;
 
             public ProjectSymbolReference(
-                AbstractAddImportCodeFixProvider<TSimpleNameSyntax> provider,
+                AbstractAddImportFeatureService<TSimpleNameSyntax> provider,
                 SymbolResult<INamespaceOrTypeSymbol> symbolResult,
                 Project project)
                 : base(provider, symbolResult)

src/Features/Core/Portable/AddImport/References/Reference.cs

@@ -13,15 +13,15 @@
 
 namespace Microsoft.CodeAnalysis.AddImport
 {
-    internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSyntax>
+    internal abstract partial class AbstractAddImportFeatureService<TSimpleNameSyntax>
     {
         private abstract class Reference : IEquatable<Reference>
         {
-            protected readonly AbstractAddImportCodeFixProvider<TSimpleNameSyntax> provider;
+            protected readonly AbstractAddImportFeatureService<TSimpleNameSyntax> provider;
             public readonly SearchResult SearchResult;
 
             protected Reference(
-                AbstractAddImportCodeFixProvider<TSimpleNameSyntax> provider,
+                AbstractAddImportFeatureService<TSimpleNameSyntax> provider,
                 SearchResult searchResult)
             {
                 this.provider = provider;

src/Features/Core/Portable/AddImport/References/SymbolReference.cs

@@ -10,7 +10,7 @@
 
 namespace Microsoft.CodeAnalysis.AddImport
 {
-    internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSyntax>
+    internal abstract partial class AbstractAddImportFeatureService<TSimpleNameSyntax>
     {
         private abstract partial class SymbolReference : Reference
         {
@@ -19,7 +19,7 @@ private abstract partial class SymbolReference : Reference
             protected abstract bool ShouldAddWithExistingImport(Document document);
 
             public SymbolReference(
-                AbstractAddImportCodeFixProvider<TSimpleNameSyntax> provider,
+                AbstractAddImportFeatureService<TSimpleNameSyntax> provider,
                 SymbolResult<INamespaceOrTypeSymbol> symbolResult)
                 : base(provider, new SearchResult(symbolResult))
             {

src/Features/Core/Portable/AddImport/SearchScopes/AllSymbolsProjectSearchScope.cs

@@ -7,7 +7,7 @@
 
 namespace Microsoft.CodeAnalysis.AddImport
 {
-    internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSyntax>
+    internal abstract partial class AbstractAddImportFeatureService<TSimpleNameSyntax>
     {
         /// <summary>
         /// SearchScope used for searching *all* the symbols contained within a project/compilation.
@@ -17,7 +17,7 @@ internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSynt
         private class AllSymbolsProjectSearchScope : ProjectSearchScope
         {
             public AllSymbolsProjectSearchScope(
-                AbstractAddImportCodeFixProvider<TSimpleNameSyntax> provider,
+                AbstractAddImportFeatureService<TSimpleNameSyntax> provider,
                 Project project,
                 bool exact,
                 CancellationToken cancellationToken)

src/Features/Core/Portable/AddImport/SearchScopes/MetadataSymbolsSearchScope.cs

@@ -8,7 +8,7 @@
 
 namespace Microsoft.CodeAnalysis.AddImport
 {
-    internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSyntax>
+    internal abstract partial class AbstractAddImportFeatureService<TSimpleNameSyntax>
     {
         private class MetadataSymbolsSearchScope : SearchScope
         {
@@ -18,7 +18,7 @@ private class MetadataSymbolsSearchScope : SearchScope
             private readonly PortableExecutableReference _metadataReference;
 
             public MetadataSymbolsSearchScope(
-                AbstractAddImportCodeFixProvider<TSimpleNameSyntax> provider,
+                AbstractAddImportFeatureService<TSimpleNameSyntax> provider,
                 Solution solution,
                 IAssemblySymbol assembly,
                 ProjectId assemblyProjectId,

src/Features/Core/Portable/AddImport/SearchScopes/ProjectSearchScope.cs

@@ -4,14 +4,14 @@
 
 namespace Microsoft.CodeAnalysis.AddImport
 {
-    internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSyntax>
+    internal abstract partial class AbstractAddImportFeatureService<TSimpleNameSyntax>
     {
         private abstract class ProjectSearchScope : SearchScope
         {
             protected readonly Project _project;
 
             public ProjectSearchScope(
-                AbstractAddImportCodeFixProvider<TSimpleNameSyntax> provider,
+                AbstractAddImportFeatureService<TSimpleNameSyntax> provider,
                 Project project,
                 bool exact,
                 CancellationToken cancellationToken)

src/Features/Core/Portable/AddImport/SearchScopes/SearchScope.cs

@@ -9,10 +9,10 @@
 
 namespace Microsoft.CodeAnalysis.AddImport
 {
-    internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSyntax>
+    internal abstract partial class AbstractAddImportFeatureService<TSimpleNameSyntax>
     {
         /// <summary>
-        /// SearchScope is used to control where the <see cref="AbstractAddImportCodeFixProvider{TSimpleNameSyntax}"/>
+        /// SearchScope is used to control where the <see cref="AbstractAddImportFeatureService{TSimpleNameSyntax}"/>
         /// searches.  We search different scopes in different ways.  For example we use 
         /// SymbolTreeInfos to search unreferenced projects and metadata dlls.  However,
         /// for the current project we're editing we defer to the compiler to do the 
@@ -21,10 +21,10 @@ internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSynt
         private abstract class SearchScope
         {
             public readonly bool Exact;
-            protected readonly AbstractAddImportCodeFixProvider<TSimpleNameSyntax> provider;
+            protected readonly AbstractAddImportFeatureService<TSimpleNameSyntax> provider;
             public readonly CancellationToken CancellationToken;
 
-            protected SearchScope(AbstractAddImportCodeFixProvider<TSimpleNameSyntax> provider, bool exact, CancellationToken cancellationToken)
+            protected SearchScope(AbstractAddImportFeatureService<TSimpleNameSyntax> provider, bool exact, CancellationToken cancellationToken)
             {
                 this.provider = provider;
                 Exact = exact;

src/Features/Core/Portable/AddImport/SearchScopes/SourceSymbolsProjectSearchScope.cs

@@ -10,7 +10,7 @@
 
 namespace Microsoft.CodeAnalysis.AddImport
 {
-    internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSyntax>
+    internal abstract partial class AbstractAddImportFeatureService<TSimpleNameSyntax>
     {
         /// <summary>
         /// SearchScope used for searching *only* the source symbols contained within a project/compilation.
@@ -21,7 +21,7 @@ private class SourceSymbolsProjectSearchScope : ProjectSearchScope
             private readonly ConcurrentDictionary<Project, AsyncLazy<IAssemblySymbol>> _projectToAssembly;
 
             public SourceSymbolsProjectSearchScope(
-                AbstractAddImportCodeFixProvider<TSimpleNameSyntax> provider,
+                AbstractAddImportFeatureService<TSimpleNameSyntax> provider,
                 ConcurrentDictionary<Project, AsyncLazy<IAssemblySymbol>> projectToAssembly,
                 Project project, bool ignoreCase, CancellationToken cancellationToken)
                 : base(provider, project, ignoreCase, cancellationToken)

src/Features/Core/Portable/AddImport/SymbolReferenceFinder.cs

@@ -16,7 +16,7 @@
 
 namespace Microsoft.CodeAnalysis.AddImport
 {
-    internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSyntax>
+    internal abstract partial class AbstractAddImportFeatureService<TSimpleNameSyntax>
     {
         private partial class SymbolReferenceFinder
         {
@@ -30,17 +30,19 @@ private partial class SymbolReferenceFinder
             private readonly ISymbol _containingTypeOrAssembly;
             private readonly ISet<INamespaceSymbol> _namespacesInScope;
             private readonly ISyntaxFactsService _syntaxFacts;
-            private readonly AbstractAddImportCodeFixProvider<TSimpleNameSyntax> _owner;
+            private readonly AbstractAddImportFeatureService<TSimpleNameSyntax> _owner;
 
             private readonly SyntaxNode _node;
             private readonly ISymbolSearchService _symbolSearchService;
+            private readonly bool _searchReferenceAssemblies;
             private readonly ImmutableArray<PackageSource> _packageSources;
 
             public SymbolReferenceFinder(
-                AbstractAddImportCodeFixProvider<TSimpleNameSyntax> owner,
+                AbstractAddImportFeatureService<TSimpleNameSyntax> owner,
                 Document document, SemanticModel semanticModel,
                 string diagnosticId, SyntaxNode node,
                 ISymbolSearchService symbolSearchService,
+                bool searchReferenceAssemblies,
                 ImmutableArray<PackageSource> packageSources,
                 CancellationToken cancellationToken)
             {
@@ -49,9 +51,16 @@ private partial class SymbolReferenceFinder
                 _semanticModel = semanticModel;
                 _diagnosticId = diagnosticId;
                 _node = node;
+
                 _symbolSearchService = symbolSearchService;
+                _searchReferenceAssemblies = searchReferenceAssemblies;
                 _packageSources = packageSources;
 
+                if (_searchReferenceAssemblies || packageSources.Length> 0)
+                {
+                    Contract.ThrowIfNull(symbolSearchService);
+                }
+
                 _containingType = semanticModel.GetEnclosingNamedType(node.SpanStart, cancellationToken);
                 _containingTypeOrAssembly = _containingType ?? (ISymbol)semanticModel.Compilation.Assembly;
                 _syntaxFacts = document.GetLanguageService<ISyntaxFactsService>();

src/Features/Core/Portable/AddImport/SymbolReferenceFinder_PackageAssemblySearch.cs

@@ -8,7 +8,7 @@
 
 namespace Microsoft.CodeAnalysis.AddImport
 {
-    internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSyntax>
+    internal abstract partial class AbstractAddImportFeatureService<TSimpleNameSyntax>
     {
         private partial class SymbolReferenceFinder
         {
@@ -60,7 +60,7 @@ private partial class SymbolReferenceFinder
                 ArrayBuilder<Reference> allReferences, TSimpleNameSyntax nameNode,
                 string name, int arity, bool isAttributeSearch, CancellationToken cancellationToken)
             {
-                if (_symbolSearchService != null)
+                if (_searchReferenceAssemblies)
                 {
                     cancellationToken.ThrowIfCancellationRequested();
                     await FindReferenceAssemblyTypeReferencesAsync(

src/Features/Core/Portable/AddImport/SymbolResult.cs

@@ -8,7 +8,7 @@
 
 namespace Microsoft.CodeAnalysis.AddImport
 {
-    internal abstract partial class AbstractAddImportCodeFixProvider<TSimpleNameSyntax>
+    internal abstract partial class AbstractAddImportFeatureService<TSimpleNameSyntax>
     {
         private struct SearchResult
         {

src/Features/VisualBasic/Portable/AddImport/VisualBasicAddImportCodeFixProvider.vb

@@ -8,6 +8,7 @@ Imports Microsoft.CodeAnalysis.AddImports
 Imports Microsoft.CodeAnalysis.CaseCorrection
 Imports Microsoft.CodeAnalysis.CodeFixes
 Imports Microsoft.CodeAnalysis.Formatting
+Imports Microsoft.CodeAnalysis.Host.Mef
 Imports Microsoft.CodeAnalysis.LanguageServices
 Imports Microsoft.CodeAnalysis.Packaging
 Imports Microsoft.CodeAnalysis.Simplification
@@ -17,7 +18,7 @@ Imports Microsoft.CodeAnalysis.VisualBasic.Syntax
 Namespace Microsoft.CodeAnalysis.VisualBasic.AddImport
     <ExportCodeFixProvider(LanguageNames.VisualBasic, Name:=PredefinedCodeFixProviderNames.AddImport), [Shared]>
     Friend Class VisualBasicAddImportCodeFixProvider
-        Inherits AbstractAddImportCodeFixProvider(Of SimpleNameSyntax)
+        Inherits AbstractAddImportCodeFixProvider
 
         Public Sub New()
         End Sub
@@ -110,6 +111,11 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.AddImport
                 Return ImmutableArray.Create(BC30002, BC30451, BC30456, BC32042, BC36593, BC32045, BC30389, BC31504, BC32016, BC36610, BC36719, BC30512, BC30390, BC42309, BC30182)
             End Get
         End Property
+    End Class
+
+    <ExportLanguageService(GetType(IAddImportFeatureService), LanguageNames.VisualBasic), [Shared]>
+    Friend Class VisualBasicAddImportFeatureService
+        Inherits AbstractAddImportFeatureService(Of SimpleNameSyntax)
 
         Protected Overrides Function CanAddImport(node As SyntaxNode, cancellationToken As CancellationToken) As Boolean
             If node.GetAncestor(Of ImportsStatementSyntax)() IsNot Nothing Then
@@ -125,9 +131,12 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.AddImport
                 node As SyntaxNode,
                 ByRef nameNode As SimpleNameSyntax) As Boolean
             Select Case diagnosticId
-                Case BC30456, BC30390, BC42309, BC30451
+                Case VisualBasicAddImportCodeFixProvider.BC30456,
+                     VisualBasicAddImportCodeFixProvider.BC30390,
+                     VisualBasicAddImportCodeFixProvider.BC42309,
+                     VisualBasicAddImportCodeFixProvider.BC30451
                     Exit Select
-                Case BC30512
+                Case VisualBasicAddImportCodeFixProvider.BC30512
                     ' look up its corresponding method name
                     Dim parent = node.GetAncestor(Of InvocationExpressionSyntax)()
                     If parent Is Nothing Then
@@ -140,13 +149,13 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.AddImport
                         node = parent.Expression
                     End If
                     Exit Select
-                Case BC36719
+                Case VisualBasicAddImportCodeFixProvider.BC36719
                     If node.IsKind(SyntaxKind.ObjectCollectionInitializer) Then
                         Return True
                     End If
 
                     Return False
-                Case BC32016
+                Case VisualBasicAddImportCodeFixProvider.BC32016
                     Dim memberAccessName = TryCast(node, MemberAccessExpressionSyntax)?.Name
                     Dim conditionalAccessName = TryCast(TryCast(TryCast(node, ConditionalAccessExpressionSyntax)?.WhenNotNull, InvocationExpressionSyntax)?.Expression, MemberAccessExpressionSyntax)?.Name
 
@@ -179,7 +188,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.AddImport
 
         Protected Overrides Function CanAddImportForNamespace(diagnosticId As String, node As SyntaxNode, ByRef nameNode As SimpleNameSyntax) As Boolean
             Select Case diagnosticId
-                Case BC30002, BC30451
+                Case VisualBasicAddImportCodeFixProvider.BC30002,
+                     VisualBasicAddImportCodeFixProvider.BC30451
                     Exit Select
                 Case Else
                     Return False
@@ -194,7 +204,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.AddImport
         End Function
 
         Protected Overrides Function CanAddImportForQuery(diagnosticId As String, node As SyntaxNode) As Boolean
-            If diagnosticId <> BC36593 Then
+            If diagnosticId <> VisualBasicAddImportCodeFixProvider.BC36593 Then
                 Return False
             End If
 
@@ -210,9 +220,16 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.AddImport
         Protected Overrides Function CanAddImportForType(
                 diagnosticId As String, node As SyntaxNode, ByRef nameNode As SimpleNameSyntax) As Boolean
             Select Case diagnosticId
-                Case BC30002, BC30451, BC32042, BC32045, BC30389, BC31504, BC36610, BC30182
+                Case VisualBasicAddImportCodeFixProvider.BC30002,
+                     VisualBasicAddImportCodeFixProvider.BC30451,
+                     VisualBasicAddImportCodeFixProvider.BC32042,
+                     VisualBasicAddImportCodeFixProvider.BC32045,
+                     VisualBasicAddImportCodeFixProvider.BC30389,
+                     VisualBasicAddImportCodeFixProvider.BC31504,
+                     VisualBasicAddImportCodeFixProvider.BC36610,
+                     VisualBasicAddImportCodeFixProvider.BC30182
                     Exit Select
-                Case BC42309
+                Case VisualBasicAddImportCodeFixProvider.BC42309
                     Select Case node.Kind
                         Case SyntaxKind.XmlCrefAttribute
                             node = CType(node, XmlCrefAttributeSyntax).Reference.DescendantNodes().OfType(Of IdentifierNameSyntax).FirstOrDefault()