public static async Task AppendLineToFileAsync(string fileName, string line) { try { #if UWP var folder = ApplicationData.Current.LocalFolder; var file = await folder.CreateFileAsync(fileName, CreationCollisionOption.OpenIfExists); await FileIO.AppendLinesAsync(file, new List <string>() { line }); #else IFolder folder = FileSystem.Current.LocalStorage; IFile file = await folder.CreateFileAsync(fileName, CreationCollisionOption.OpenIfExists); await file.AppendAllLinesAsync(new List <string>() { line }); #endif } catch { /* Avoid any exception at this point. */ } }