c#中oracle的to_date函数使用方法

public static DataTable Query(){  const string sSql = "select xh,lsh,name from table where gxsj>to_date(:gxsj,'yyyy-MM-dd HH24:mi:ss')";  OracleParameter[] parameters = {new OracleParameter(":gxsj", OracleType.VarChar, 10)};  parameters[0].Value = DateTime.Now.AddHours(-3).ToString("yyyy-MM-dd HH") + ":00:00";  return DBUtility.DbHelperOra.Query(sSql, parameters).Tables[0];}

public static string GetHphm(string sClsbdh){  const string sSql = "select name from table where sj>to_date(:yxsj,'yyyy-MM-dd')";  OracleParameter[] paramters = {new OracleParameter("sj", OracleType.VarChar, 10)};  paramters[0].Value = DateTime.Now.ToString("yyyy-MM-dd");   using (var mReader = DbHelperOra.ExecuteReader(sSql, paramters))  {      if (mReader.Read())      {      return mReader["name"].ToString();      }  }   return "";}