private void btn_PreviewQuestion_Click(object sender, EventArgs e)
{
PreviewQuestion Preview = new PreviewQuestion();
Preview.QuestionPreview = txt_ContentQuestion.Text;
foreach (Answer_OnlyOneSelect onechoice in flp_Answer.Controls)
{
Preview.AnswerPreview.Add(onechoice.txt_Answercontent.Text);
}
Preview.ShowDialog();
}