UsingsAnalyzerCodeFixProvider

UsingsAnalyzerCodeFixProvider.cs

private static async Task<Document> GetTransformedDocumentAsync(Document document, Diagnostic diagnostic, CancellationToken cancellationToken)
{
    try
    {
        SyntaxNode root = await document.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
        var usings = root.DescendantNodes().OfType<UsingDirectiveSyntax>().ToList();
        var orderedUsings = usings.OrderBy(o => new string(o.Name.ToString().TakeWhile(c => c != '.').ToArray()))
            .ThenBy(o => o.Name.ToString().Length)
            .ToList();

        var documentEditor = await DocumentEditor.CreateAsync(document, cancellationToken);
        for (var index = 0; index < usings.Count; index++)
        {
            var usingStatement = usings[index];
            var usingDirectiveSyntax = orderedUsings[index];
            if (index > 0)
            {
                var currentNamespace = GetAssemblyNameFromNamespace(orderedUsings[index]);
                var lastNamespace = GetAssemblyNameFromNamespace(orderedUsings[index - 1]);
                if (currentNamespace != lastNamespace) //add a new line between usings from different assemblies
                {
                    usingDirectiveSyntax =
                        usingDirectiveSyntax.WithLeadingTrivia(
                            SyntaxTriviaList.Create(SyntaxFactory.CarriageReturnLineFeed));
                }
            }
            documentEditor.ReplaceNode(usingStatement, usingDirectiveSyntax);
        }
        return documentEditor.GetChangedDocument();
    }
    catch (Exception e)
    {
        Console.WriteLine(e);
        return document;
    }
}

private static string GetAssemblyNameFromNamespace(UsingDirectiveSyntax usingDirective)
{
    return new string(usingDirective.ToString().Split(' ')[1].TakeWhile(c => c != '.').ToArray()).Trim(';');
}