CSharpUseIndexOperatorCodeFixProvider.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.Immutable;
using System.Composition;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.CodeActions;
using Microsoft.CodeAnalysis.CodeFixes;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Diagnostics;
using Microsoft.CodeAnalysis.Editing;
using Microsoft.CodeAnalysis.Shared.Extensions;

namespace Microsoft.CodeAnalysis.CSharp.UseIndexOrRangeOperator
{
    using System.Linq;
    using static Helpers;

    [ExportCodeFixProvider(LanguageNames.CSharp), Shared]
    internal class CSharpUseIndexOperatorCodeFixProvider : SyntaxEditorBasedCodeFixProvider
    {
        public override ImmutableArray<string> FixableDiagnosticIds { get; } =
            ImmutableArray.Create(IDEDiagnosticIds.UseIndexOperatorDiagnosticId);
 
        public override Task RegisterCodeFixesAsync(CodeFixContext context)
        {
            context.RegisterCodeFix(new MyCodeAction(
                c => FixAsync(context.Document, context.Diagnostics[0], c)),
                context.Diagnostics);

            return Task.CompletedTask;
        }

        protected override Task FixAllAsync(
            Document document, ImmutableArray<Diagnostic> diagnostics,
            SyntaxEditor editor, CancellationToken cancellationToken)
        {
            // Process diagnostics from innermost to outermost in case any are nested.
            foreach (var diagnostic in diagnostics.OrderByDescending(d => d.Location.SourceSpan.Start))
            {
                var node = diagnostic.Location.FindNode(getInnermostNodeForTie: true, cancellationToken);

                editor.ReplaceNode(
                    node,
                    (currentNode, _) => IndexExpression(((BinaryExpressionSyntax)currentNode).Right));
            }

            return Task.CompletedTask;
        }

        private class MyCodeAction : CodeAction.DocumentChangeAction
        {
            public MyCodeAction(Func<CancellationToken, Task<Document>> createChangedDocument) 
                : base(FeaturesResources.Use_index_operator, createChangedDocument, FeaturesResources.Use_index_operator)
            {
            }
        }
    }
}