public void AddAttachment()
        {
            // Create a file to attach with sample text
            var filePath = Path.Combine(Path.GetTempPath(), Path.GetRandomFileName());

            using (FileStream fstream = File.Create(filePath))
            {
                using (StreamWriter swriter = new StreamWriter(fstream))
                {
                    swriter.Write("Sample attachment text");
                }
            }

            // Upload attachment
            AttachmentReference attachment = WitClient.CreateAttachmentAsync(filePath).Result;

            Console.WriteLine("Attachment created");
            Console.WriteLine($"ID: {attachment.Id}");
            Console.WriteLine($"URL: '{attachment.Url}'");
            Console.WriteLine();

            // Get an existing work item and add the attachment to it
            WorkItem          wi = WitClient.GetWorkItemAsync(this.WorkItemsAdded.First()).Result;
            JsonPatchDocument attachmentPatchDocument = new JsonPatchDocument
            {
                new JsonPatchOperation()
                {
                    Operation = Operation.Add,
                    Path      = "/relations/-",
                    Value     = new
                    {
                        rel        = "AttachedFile",
                        url        = attachment.Url,
                        attributes = new
                        {
                            comment = "Attached a file"
                        }
                    }
                }
            };

            var attachments = wi.Relations?.Where(r => r.Rel == "AttachedFile") ?? new List <WorkItemRelation>();
            var previousAttachmentsCount = attachments.Count();

            var result = WitClient.UpdateWorkItemAsync(attachmentPatchDocument, wi.Id.Value).Result;

            var newAttachments      = result.Relations?.Where(r => r.Rel == "AttachedFile");
            var newAttachmentsCount = newAttachments.Count();

            Console.WriteLine($"Updated Existing Work Item: '{wi.Id}'. Had {previousAttachmentsCount} attachments, now has {newAttachmentsCount}");
            Console.WriteLine();
        }