c#中关于日期转换的方法，求指导，求教育，我想只查询到月，应该怎么改啊！！！！
 private string date()
        {
            string date = this.dateTimePicker1.Text.Replace('年', '-').Replace('月', '-').Replace('日', ' ');
            //string date = this.dateTimePicker1.Text.Replace('年', '-').Replace('月', ' ');
            string dateNew = string.Empty;
            char[] C ={ '-' };
            string[] dateinfo = date.Split(C);
            if (dateinfo[1].Trim().ToString().Length <= 1)
            {
                dateNew += dateinfo[0].ToString() + "-0" + dateinfo[1].ToString();
            }
            else
            {
                dateNew += dateinfo[0].ToString() + "-" + dateinfo[1].ToString();
            }

            if (dateinfo[2].Trim().ToString().Length <= 1)
            {
                dateNew += "-0" + dateinfo[2].ToString();
            }
            else
            {
                dateNew += "-" + dateinfo[2].ToString();
            }

            return dateNew;
        }