Date Validation

·         Field name is = tbToDate there only 1 field and I have code for 2 fields… bcz correct me…

private string  CreateWhereStr()

            {

                  string  strWhere= "";

                  string  strWhereFromDate = tbFromDate.Text.ToString();

                  string  strWhereEndDate  = tbToDate.Text.ToString();

                  try

                  {    

                        if (( strWhereFromDate.ToString() != "" )   && (strWhereEndDate.ToString() != ""  ))

                        {

                              DateTime  WhereFromDate = ConvertDate(strWhereFromDate) ;

                              DateTime  WhereEndDate =  ConvertDate(tbToDate.Text.ToString()) ;

                              if (WhereFromDate.Date > WhereEndDate.Date )

                              {

                                    throw new ArgumentException(" ‘To Date’ must be bigger than ‘From Date’.");

                              }

                              else

                              {

                                    strWhere = strWhere +  "  AND to_date(EXPIRE_DATE) > to_date('" + strWhereFromDate.ToString() +  "','dd/MM/yyyy') AND to_date(EXPIRE_DATE) < to_date('" +   strWhereEndDate.ToString()+ "','dd/MM/yyyy')"  ;

                              }

                        }

                        else if (( strWhereFromDate.ToString() != ""  ) && (strWhereEndDate.ToString() == ""  ))

                        {

                              strWhere = strWhere +  " AND  to_date(EXPIRE_DATE) > to_date('" + strWhereFromDate.ToString()+ " ' ,'dd/MM/yyyy')"  ;

                        }

                        else if (( strWhereFromDate.ToString() == ""  ) && (strWhereEndDate.ToString() != ""  ))

                        {

                              strWhere = strWhere +  " AND to_date(EXPIRE_DATE) < to_date ('" +   strWhereEndDate.ToString()+ " ' ,'dd/MM/yyyy')"  ;

                        }

                  }

                  catch( Exception ex)

                  {

                        throw new ArgumentException(ex.Message.ToString()) ;

                  }

                  return strWhere ;

            }