c# 转换成时间类型

if (rngFound.Value.ToString().Contains("/"))
{
closingdate = rngFound.Value;
}
else if (rngFound.Value.ToString().Contains("-"))
{
closingdate = Convert.ToDateTime(rngFound.Value.ToString());
}
else
{
closingdate = DateTime.ParseExact(rngFound.Value2.ToString(), "yyyyMMdd", System.Globalization.CultureInfo.CurrentCulture);
}