fixProvider.

src/Features/Core/Portable/CodeFixes/PredefinedCodeFixProviderNames.cs

@@ -38,6 +38,7 @@ internal static class PredefinedCodeFixProviderNames
         public const string RemoveUnnecessaryImports = "Remove Unnecessary Usings or Imports";
         public const string RenameTracking = "Rename Tracking";
         public const string SimplifyNames = "Simplify Names";
+        public const string SimplifyNullCheck = nameof(SimplifyNullCheck);
         public const string SpellCheck = "Spell Check";
         public const string Suppression = nameof(Suppression);
         public const string AddOverloads = "Add Overloads to member";

src/Features/Core/Portable/Diagnostics/Analyzers/IDEDiagnosticIds.cs

@@ -19,6 +19,7 @@ internal static class IDEDiagnosticIds
         public const string PreferIntrinsicPredefinedTypeInMemberAccessDiagnosticId = "IDE0013";
         public const string PreferFrameworkTypeInDeclarationsDiagnosticId = "IDE0014";
         public const string PreferFrameworkTypeInMemberAccessDiagnosticId = "IDE0015";
+        public const string SimplifyNullCheckDiagnosticId = "IDE0016";
 
         // Analyzer error Ids
         public const string AnalyzerChangedId = "IDE1001";

src/Features/Core/Portable/Features.csproj

@@ -93,6 +93,7 @@
     <Compile Include="AddMissingReference\AbstractAddMissingReferenceCodeFixProvider.cs" />
     <Compile Include="AddMissingReference\CodeAction.cs" />
     <Compile Include="SimplifyNullCheck\SimplifyNullCheckAnalyzer.cs" />
+    <Compile Include="SimplifyNullCheck\SimplifyNullCheckCodeFixProvider.cs" />
     <Compile Include="Structure\BlockTypes.cs" />
     <Compile Include="CodeLens\CodeLensReferencesServiceFactory.cs" />
     <Compile Include="Structure\Syntax\BlockStructureExtensions.cs" />

src/Features/Core/Portable/SimplifyNullCheck/SimplifyNullCheckAnalyzer.cs

@@ -38,7 +38,8 @@ internal class SimplifyNullCheckAnalyzer : DiagnosticAnalyzer, IBuiltInAnalyzer
         private static readonly LocalizableString s_localizableTitle = new LocalizableResourceString(nameof(FeaturesResources.Simplify_null_check), FeaturesResources.ResourceManager, typeof(FeaturesResources));
         private static readonly LocalizableString s_localizableMessage = new LocalizableResourceString(nameof(FeaturesResources.Simplify_null_check), WorkspacesResources.ResourceManager, typeof(WorkspacesResources));
 
-        private static readonly DiagnosticDescriptor s_descriptor = new DiagnosticDescriptor(IDEDiagnosticIds.PopulateSwitchDiagnosticId,
+        private static readonly DiagnosticDescriptor s_descriptor = new DiagnosticDescriptor(
+            IDEDiagnosticIds.SimplifyNullCheckDiagnosticId,
             s_localizableTitle,
             s_localizableMessage,
             DiagnosticCategory.Style,
@@ -122,8 +123,8 @@ private void AnalyzeOperation(OperationAnalysisContext operationContext)
             // Ok, there were no intervening writes.  This check+assignment can be simplified.
 
             var allLocations = ImmutableArray.Create(
-                throwOperation.Syntax.GetLocation(),
-                expressionStatement.Syntax.GetLocation(),
+                ifOperation.Syntax.GetLocation(),
+                throwOperation.ThrownObject.Syntax.GetLocation(),
                 assignmentExpression.Value.Syntax.GetLocation());
 
             operationContext.ReportDiagnostic(

src/Features/Core/Portable/SimplifyNullCheck/SimplifyNullCheckCodeFixProvider.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.Collections.Immutable;
+using System.Composition;
+using System.Linq;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.CodeActions;
+using Microsoft.CodeAnalysis.CodeFixes;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Microsoft.CodeAnalysis.Editing;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.SimplifyNullCheck
+{
+    [ExportCodeFixProvider(LanguageNames.CSharp,
+        Name = PredefinedCodeFixProviderNames.SimplifyNullCheck), Shared]
+    internal class SimplifyNullCheckCodeFixProvider : CodeFixProvider
+    {
+        public override ImmutableArray<string> FixableDiagnosticIds
+            => ImmutableArray.Create(IDEDiagnosticIds.SimplifyNullCheckDiagnosticId);
+
+        public override Task RegisterCodeFixesAsync(CodeFixContext context)
+        {
+            var diagnostic = context.Diagnostics.First();
+            context.RegisterCodeFix(
+                new MyCodeAction(c => FixAsync(context.Document, diagnostic, c)),
+                diagnostic);
+
+            return SpecializedTasks.EmptyTask;
+        }
+
+        private async Task<Document> FixAsync(
+            Document document, 
+            Diagnostic diagnostic, 
+            CancellationToken cancellationToken)
+        {
+            var root = await document.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
+
+            var ifStatement = root.FindNode(diagnostic.AdditionalLocations[0].SourceSpan);
+            var throwStatementExpression = root.FindNode(diagnostic.AdditionalLocations[1].SourceSpan);
+            var assignmentValue = root.FindNode(diagnostic.AdditionalLocations[2].SourceSpan);
+
+            var editor = new SyntaxEditor(root, document.Project.Solution.Workspace);
+            var generator = editor.Generator;
+
+            // First, remote the if-statement entirely.
+            editor.RemoveNode(ifStatement);
+
+            // Now, update the assignemnt value to go from 'a' to 'a ?? throw ...'.
+            editor.ReplaceNode(assignmentValue,
+                generator.CoalesceExpression(assignmentValue,
+                generator.ThrowExpression(throwStatementExpression)));
+
+            var newRoot = editor.GetChangedRoot();
+            return document.WithSyntaxRoot(newRoot);
+        }
+
+        private class MyCodeAction : CodeAction.DocumentChangeAction
+        {
+            public MyCodeAction(
+                Func<CancellationToken, Task<Document>> createChangedDocument) 
+                : base(FeaturesResources.Simplify_null_check, createChangedDocument, FeaturesResources.Simplify_null_check)
+            {
+            }
+        }
+    }
+}