private async void GetUserByIdClick(object sender, RoutedEventArgs e) { var client = new WebApiSender(urlAddress); string[] formats = { "N", "D", "B", "P", "X" }; Guid result; try { Guid.TryParseExact(txtId.Text, "D", out result); var files = await client.GetPersonAsync(result); var buffer = Convert.FromBase64String(files.Photo); imgPhoto.Source = ByteToImage(buffer); } catch (NullReferenceException err) { MessageBox.Show(err.Message); } }