public void AddChoice(Choice choice, string topicId, string username)
{
var topic = dac.GetTopic(x => x.id == topicId);
var now = DateTime.UtcNow;
string newid = Guid.NewGuid().ToString();
Choice newChoice = new Choice()
{
Id = newid,
Name = choice.Name,
CraeteBy = username,
};
var choicelist = topic.ChoiceList.ToList();
choicelist.Add(newChoice);
topic.ChoiceList = choicelist;
dac.UpdateTopic(topic);
}