{"ORA-01008: 并非所有变量都已绑定"} 找不到问题，请帮帮忙！！！

Question

public DataSet Selectdata(string Order_number)
{

      string str =@"select VEH_PLATE_NUMBER,VEH_PLATE_COLOR,VEH_TYPE,VEH_BRAND_CODE from WEB_BOOKED_VEHICLES  where Order_NO=:ORDERNO";
       OracleParameter []prara = new OracleParameter[]
       {
        new OracleParameter(":ORDERNO",Order_number)
      };

       return oracleHelper.ExecuteProcDataSet(str,prara);
   }

Answer 1

OracleParameter[] prara = new OracleParameter[]{
new OracleParameter(":ORDERNO",OracleType.VarChar,50)
};
prara[0].Value = Order_number;