private DocumentFile OpenCore()

in Samples-NetCore/DotNetPad/DotNetPad.Applications/Controllers/FileController.cs [246:286]
35 lines of code
8 McCabe index (conditional complexity)

        private DocumentFile OpenCore(string fileName = null, bool setActiveDocument = true)
        {
            if (string.IsNullOrEmpty(fileName))
            {
                var result = fileDialogService.ShowOpenFileDialog(shellService.ShellView, allFilesType);
                if (result.IsValid)
                {
                    fileName = result.FileName;
                }
            }

            if (string.IsNullOrEmpty(fileName))
            {
                return null;
            }

            // Check if document is already opened
            var document = fileService.DocumentFiles.SingleOrDefault(d => d.FileName == fileName);
            if (document == null)
            {
                string fileExtension = Path.GetExtension(fileName);
                if (!new[] { ".cs", ".vb" }.Contains(fileExtension))
                {
                    Trace.TraceError(string.Format(CultureInfo.InvariantCulture,
                        "The extension of the file '{0}' is not supported.", fileName));
                    messageService.ShowError(shellService.ShellView, string.Format(CultureInfo.CurrentCulture, Resources.OpenFileUnsupportedExtension, fileName));
                    return null;
                }

                var documentType = fileExtension == ".cs" ? DocumentType.CSharp : DocumentType.VisualBasic;
                document = new DocumentFile(documentType, LoadDocumentContent)
                {
                    FileName = fileName
                };

                fileService.AddDocument(document);
            }

            if (setActiveDocument) { ActiveDocumentFile = document; }
            return document;
        }