Simplifying code now that it doesn't need to support multiple purposes.

src/Features/CSharp/Portable/CodeFixes/Async/CSharpAddAwaitCodeFixProvider.cs

@@ -38,19 +38,17 @@ internal class CSharpAddAwaitCodeFixProvider : AbstractAddAwaitCodeFixProvider
 
         public override ImmutableArray<string> FixableDiagnosticIds => ImmutableArray.Create(CS0029, CS4014, CS4016);
 
-        protected override async Task<IList<DescriptionAndNode>> GetDescriptionsAndNodesAsync(
+        protected override async Task<DescriptionAndNode> GetDescriptionAndNodeAsync(
             SyntaxNode root, SyntaxNode oldNode, SemanticModel semanticModel, Diagnostic diagnostic, Document document, CancellationToken cancellationToken)
         {
             var newRoot = await GetNewRootAsync(
                 root, oldNode, semanticModel, diagnostic, document, cancellationToken).ConfigureAwait(false);
             if (newRoot == null)
             {
-                return null;
+                return default(DescriptionAndNode);
             }
 
-            return SpecializedCollections.SingletonList(new DescriptionAndNode(
-                CSharpFeaturesResources.Insert_await,
-                newRoot));
+            return new DescriptionAndNode(CSharpFeaturesResources.Insert_await, newRoot);
         }
 
         private Task<SyntaxNode> GetNewRootAsync(

src/Features/Core/Portable/CodeFixes/Async/AbstractAddAwaitCodeFixProvider.cs

@@ -10,31 +10,23 @@ namespace Microsoft.CodeAnalysis.CodeFixes.Async
 {
     internal abstract partial class AbstractAddAwaitCodeFixProvider : AbstractAsyncCodeFix
     {
-        protected abstract Task<IList<DescriptionAndNode>> GetDescriptionsAndNodesAsync(
+        protected abstract Task<DescriptionAndNode> GetDescriptionAndNodeAsync(
             SyntaxNode root, SyntaxNode oldNode, SemanticModel semanticModel, Diagnostic diagnostic, Document document, CancellationToken cancellationToken);
 
-        protected override async Task<IList<CodeAction>> GetCodeActionsAsync(
+        protected override async Task<CodeAction> GetCodeActionAsync(
             SyntaxNode root, SyntaxNode node, Document document, Diagnostic diagnostic, CancellationToken cancellationToken)
         {
             var semanticModel = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
 
-            var data = await this.GetDescriptionsAndNodesAsync(root, node, semanticModel, diagnostic, document, cancellationToken).ConfigureAwait(false);
-            if (data == null)
+            var data = await this.GetDescriptionAndNodeAsync(root, node, semanticModel, diagnostic, document, cancellationToken).ConfigureAwait(false);
+            if (data.Node == null)
             {
                 return null;
             }
 
-            var result = new List<CodeAction>();
-
-            foreach (var item in data)
-            {
-                var action = new MyCodeAction(
-                    item.Description,
-                    c => Task.FromResult(document.WithSyntaxRoot(item.Node)));
-                result.Add(action);
-            }
-
-            return result;
+            return new MyCodeAction(
+                data.Description,
+                c => Task.FromResult(document.WithSyntaxRoot(data.Node)));
         }
 
         protected static bool TryGetExpressionType(

src/Features/Core/Portable/CodeFixes/Async/AbstractAsyncCodeFix.cs

@@ -12,7 +12,7 @@ namespace Microsoft.CodeAnalysis.CodeFixes.Async
 {
     internal abstract partial class AbstractAsyncCodeFix : CodeFixProvider
     {
-        protected abstract Task<IList<CodeAction>> GetCodeActionsAsync(
+        protected abstract Task<CodeAction> GetCodeActionAsync(
             SyntaxNode root, SyntaxNode node, Document document, Diagnostic diagnostic, CancellationToken cancellationToken);
 
         public sealed override async Task RegisterCodeFixesAsync(CodeFixContext context)
@@ -27,9 +27,9 @@ public sealed override async Task RegisterCodeFixesAsync(CodeFixContext context)
 
             var diagnostic = context.Diagnostics.FirstOrDefault();
 
-            var codeActions = await GetCodeActionsAsync(
+            var codeAction = await GetCodeActionAsync(
                 root, node, context.Document, diagnostic, context.CancellationToken).ConfigureAwait(false);
-            context.RegisterFixes(codeActions, context.Diagnostics);
+            context.RegisterCodeFix(codeAction, context.Diagnostics);
         }
 
         private bool TryGetNode(SyntaxNode root, TextSpan span, out SyntaxNode node)

src/Features/Core/Portable/CodeFixes/Async/AbstractChangeToAsyncCodeFixProvider.cs

 // Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
 using System;
-using System.Collections.Generic;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.CodeActions;
-using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.CodeFixes.Async
 {
@@ -14,23 +12,23 @@ internal abstract partial class AbstractChangeToAsyncCodeFixProvider : AbstractA
         protected abstract Task<string> GetDescription(Diagnostic diagnostic, SyntaxNode node, SemanticModel semanticModel, CancellationToken cancellationToken);
         protected abstract Task<Tuple<SyntaxTree, SyntaxNode>> GetRootInOtherSyntaxTree(SyntaxNode node, SemanticModel semanticModel, Diagnostic diagnostic, CancellationToken cancellationToken);
 
-        protected override async Task<IList<CodeAction>> GetCodeActionsAsync(
+        protected override async Task<CodeAction> GetCodeActionAsync(
             SyntaxNode root, SyntaxNode node, Document document, Diagnostic diagnostic, CancellationToken cancellationToken)
         {
             var semanticModel = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
 
             var result = await GetRootInOtherSyntaxTree(node, semanticModel, diagnostic, cancellationToken).ConfigureAwait(false);
-            if (result != null)
+            if (result == null)
             {
-                var syntaxTree = result.Item1;
-                var newRoot = result.Item2;
-                var otherDocument = document.Project.Solution.GetDocument(syntaxTree);
-                return SpecializedCollections.SingletonList<CodeAction>(new MyCodeAction(
-                    await this.GetDescription(diagnostic, node, semanticModel, cancellationToken).ConfigureAwait(false),
-                    token => Task.FromResult(otherDocument.WithSyntaxRoot(newRoot))));
+                return null;
             }
 
-            return null;
+            var syntaxTree = result.Item1;
+            var newRoot = result.Item2;
+            var otherDocument = document.Project.Solution.GetDocument(syntaxTree);
+            return new MyCodeAction(
+                await this.GetDescription(diagnostic, node, semanticModel, cancellationToken).ConfigureAwait(false),
+                token => Task.FromResult(otherDocument.WithSyntaxRoot(newRoot)));
         }
 
         private class MyCodeAction : CodeAction.DocumentChangeAction

src/Features/VisualBasic/Portable/CodeFixes/Async/VisualBasicAddAwaitCodeFixProvider.vb

@@ -29,16 +29,14 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.CodeFixes.Async
             End Get
         End Property
 
-        Protected Overrides Async Function GetDescriptionsAndNodesAsync(root As SyntaxNode, oldNode As SyntaxNode, semanticModel As SemanticModel, diagnostic As Diagnostic, document As Document, cancellationToken As CancellationToken) As Task(Of IList(Of DescriptionAndNode))
+        Protected Overrides Async Function GetDescriptionAndNodeAsync(root As SyntaxNode, oldNode As SyntaxNode, semanticModel As SemanticModel, diagnostic As Diagnostic, document As Document, cancellationToken As CancellationToken) As Task(Of DescriptionAndNode)
             Dim newRoot = Await GetNewRootAsync(
                 root, oldNode, semanticModel, diagnostic, document, cancellationToken).ConfigureAwait(False)
             If newRoot Is Nothing Then
                 Return Nothing
             End If
 
-            Return SpecializedCollections.SingletonList(New DescriptionAndNode(
-                VBFeaturesResources.Insert_Await,
-                newRoot))
+            Return New DescriptionAndNode(VBFeaturesResources.Insert_Await, newRoot)
         End Function
 
         Private Function GetNewRootAsync(root As SyntaxNode, oldNode As SyntaxNode, semanticModel As SemanticModel, diagnostic As Diagnostic, document As Document, cancellationToken As CancellationToken) As Task(Of SyntaxNode)