如果把从页面控件输入的日期，转换成日期型数据并进行数据查询

Question

我用 
start_date = "";
convert.todatetime(start_date); 怎么总是报错呀

Answer 1

start_date不可以为空呢。还有大小写哦

Answer 2

string start = start_year.SelectedValue + "-" + start_month.SelectedValue + "-" + start_day.SelectedValue;
            string end = end_year.SelectedValue+"-"+end_month.SelectedValue+"-"+end_day.SelectedValue;
            DateTime start_date = new DateTime();
            start_date = Convert.ToDateTime(start.ToString());
            DateTime end_date = new DateTime();
            end_date = Convert.ToDateTime(end.ToString());

Answer 3

string start = start_year.SelectedValue + "-" + start_month.SelectedValue + "-" + start_day.SelectedValue;
            string end = end_year.SelectedValue+"-"+end_month.SelectedValue+"-"+end_day.SelectedValue;
            DateTime start_date = new DateTime();
            start_date = Convert.ToDateTime(start.ToString());
            DateTime end_date = new DateTime();
            end_date = Convert.ToDateTime(end.ToString());
string start_string = start_date.ToShortDateString();
string end_string = end_date.ToShortDateString();