private async void Button2_Click(object sender, MouseEventArgs e) { list_box.Items.Clear(); var sfd = new SaveFileDialog { DefaultExtension = "txt", InitialDirectory = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), Title = "Save this file" }; sfd.AddFilter("All Files", "*"); sfd.AddFilter("Image Files", "png", "gif", "jpg", "jpeg"); sfd.AddFilter("Text Files", "txt", "log"); if ((await sfd.ShowDialog(FindForm())) == DialogResult.OK) { foreach (var file in sfd.FileNames) { list_box.Items.Add(file); } } }