Non ho trovato un modo per farlo usando Varchar2 Datatype. Quindi, sto dando la risposta usando Date Datatype.
if (dateTo.Minute > 30)
minToInt = 30;
else
minToInt = 00;
dateFrom = DateTime.Now;
dateTo = DateTime.Now;
DateTime dateFrom = new DateTime(DateTime.Now.Year, DateTime.Now.Month, DateTime.Now.Day, dateFrom.Hour, 00, 00);
DateTime dateTo = new DateTime(DateTime.Now.Year, DateTime.Now.Month, DateTime.Now.Day, dateTo.Hour, minToInt, 00);
////////FROM DATE/////////
OracleParameter fromDateParameter = new OracleParameter();
fromDateParameter.OracleDbType = OracleDbType.Date;
fromDateParameter.Value = dateFrom;
////////TO DATE/////////
OracleParameter toDateParameter = new OracleParameter();
toDateParameter.OracleDbType = OracleDbType.Date;
toDateParameter.Value = dateTo;
this.oracleDataAdapter4.SelectCommand = new OracleCommand("
SELECT DISTINCT (LOG.RID) FROM LOG WHERE LOG.TIMESTAMP
BETWEEN :fromDateParameter
AND :toDateParameter)", oracleConnection4);
oracleDataAdapter4.SelectCommand.Parameters.Add(fromDateParameter);
oracleDataAdapter4.SelectCommand.Parameters.Add(toDateParameter);
this.oracleDataAdapter4.Fill(event11);
Non confonderti con la convalida if/else minute, è solo per il mio scopo di query.