private string CreateSession(string fileName) { string json = JsonConvert.SerializeObject(new { item = new Dictionary <string, string> { { "@microsoft.graph.conflictBehavior", "replace" } } }); string folderPath = GetFolderUrl(FolderID); string url = URLHelpers.BuildUri("https://graph.microsoft.com", $"/v1.0/{folderPath}:/{fileName}:/createUploadSession"); AllowReportProgress = false; string response = SendRequest(HttpMethod.POST, url, json, RequestHelpers.ContentTypeJSON, headers: GetAuthHeaders()); AllowReportProgress = true; OneDriveUploadSession session = JsonConvert.DeserializeObject <OneDriveUploadSession>(response); if (session != null) { return(session.uploadUrl); } return(null); }