whats going wrong with my code about database

Scripting
1

Hello,guys

who can tell me whats going wrong with the following code

import System;
import System.Data;
import System.Data.Odbc;
import UnityEditor;
private var read;
private var con;
private var yourQuery;
private var oCon : OdbcConnection;
private var oCmd : OdbcCommand;
private var dtYourData : DataTable;
private var rData1 : OdbcDataReader;
function Update () {
}
function Start() {
var read= “e:/unity/unity_test.mdb”;
var con = “Driver={Microsoft Access Driver (*.mdb)}; DBQ=”+read;
var select =" SELECT * FROM data;" ;
var oCon : OdbcConnection = new OdbcConnection(con);
var oCmd1: OdbcCommand = new OdbcCommand(select,oCon);
oCon.Open();
var rData1 :OdbcDataReader= oCmd1.ExecuteReader();

"

And I got the error messages

"NullReferenceException: Object reference not set to an instance of an object
System.Data.Odbc.OdbcDataReader.GetPrimaryKeys (System.String catalog, System.String schema, System.String table)
System.Data.Odbc.OdbcDataReader.GetSchemaTable ()
System.Data.Odbc.OdbcDataReader…ctor (System.Data.Odbc.OdbcCommand command, CommandBehavior behavior)
System.Data.Odbc.OdbcDataReader…ctor (System.Data.Odbc.OdbcCommand command, CommandBehavior behavior, Int32 recordAffected)
(wrapper remoting-invoke-with-check) System.Data.Odbc.OdbcDataReader:.ctor (System.Data.Odbc.OdbcCommand,System.Data.CommandBehavior,int)
System.Data.Odbc.OdbcCommand.ExecuteReader (CommandBehavior behavior)
System.Data.Odbc.OdbcCommand.ExecuteReader ()
(wrapper remoting-invoke-with-check) System.Data.Odbc.OdbcCommand:ExecuteReader ()
database.Start () (at Assets\Standard Assets\Scripts\database.js:39)
"
If I change the “select” context with “DELETE FROM data”,and that get no problems,why? Thank you for your focus.

2

your problem is on line 39 of database.js, you get a NullReferenceException which means something is not found.

3

I see ,but how to solve it,I try in many ways,but fail,it puzzled me all the time.

4

What’s line 39?

5

The code is

var rData1 :OdbcDataReader= oCmd1.ExecuteReader();

6

oCmd1 is null.

I’ve never worked with whatever implementation of databases this is,
but,

Don’t you need to open the connection to the database before you start asking it questions?

7

Thank you !! Now it works well. I just copy two files into the Assets Foder.