Problem with dataset

coolslayerlies · April 2nd, 2009, 08:34 AM

hi i've only being studying programming for a year and a half in college so please excuse any stupid questions lol. at college i've been doing a project on vb.net 2005 but at home i have 2008. at college this code works but at home it doesnt i cant work it out.

Code:

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Call Openuserdatabase()

        SQL = "SELECT * FROM tblUserInformation"

        da = New OleDb.OleDbDataAdapter(Sql, con2)

        da.Fill(ds, "Users")
    End Sub

    Private Sub btnLogIn_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnLogIn.Click
        Do While iCount <= (ds.Tables("Users").Rows.Count) - 1
            If txtUsername.Text = ds.Tables("Users").Rows(iCount).Item(4) _
            Then
                If txtPassword.Text = ds.Tables("Users").Rows(iCount).Item(5) _
                Then
                    UserRow = iCount
                    frmSelect.Show()
                    Me.Close()
                    Exit Do
                Else
                    MsgBox("Please enter correct password")
                    intLoginCheck = intLoginCheck + 1
                    txtPassword.SelectAll()
                    txtPassword.Focus()
                    Exit Do
                End If
            Else
                iCount = iCount + 1
                If iCount = (ds.Tables("Users").Rows.Count) _
                Then
                    MsgBox("User not found")
                    txtUsername.Text = ""
                    txtUsername.Focus()
                    txtPassword.Text = ""
                    Exit Sub
                End If
            End If
        Loop

It keeps coming back with NullReferenceException was unhandled - object reference not set to an instance of an object. the coding for the connection is in a module and should produce a message box saying the connection is ok after it connects but no message box appears before the first form loads like it does at college. hers the code for the connection:

Code:

Public con As New OleDb.OleDbConnection
    Public con2 As New OleDb.OleDbConnection
    Public da As OleDb.OleDbDataAdapter
    Public ds As New DataSet
    Public ds2 As New DataSet
    Public ds3 As New DataSet
    Public UserRow As Integer

    Public iCount As Integer

    Public Sub Opendatabase()
        con.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source = F:\Rhys Crap\tblCriminal.mdb"

        con.Open()
        MsgBox("Connection OK")
    End Sub
    Public Sub Closedatabase()

        con.Close()
        MsgBox("Connection Closed")
    End Sub
    Public Sub Openuserdatabase()
        con2.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source = F:\Rhys Crap\tblUsers.mdb"

        con2.Open()
        MsgBox("Connection OK")
    End Sub

the path for the connection is right so i can't work out what is wrong and i need this to work so i can test the rest of my project. please help me

(edit) ok so i've just downloaded 2005 but it still wont work on that. could it be that my system is running on 64bit?

gbianchi · April 2nd, 2009, 11:17 AM

Hello..

Did you trace your code to find out what object is failling?? (or at least where it fails??)

Also, do you have your database in this paht = F:\Rhys Crap\tblCriminal.mdb???

coolslayerlies · April 2nd, 2009, 11:23 AM

the path is right and im sorry i forgot to put that the error came up with

Code:

Do While iCount <= (ds.Tables("Users").Rows.Count) - 1

and i think the problem must lie with the connection because the msgbox doesn't appear before the form loads like it did at college

gbianchi · April 2nd, 2009, 11:33 AM

The problem is that is never go through the load procedure...

You don't have any error in your code?? no line marked red anywhere???

What happens if you doubleclick on your form?? it goes to the load procedure or to another part?? If you set a breakpoint in the load form do you see the code stopping there??

coolslayerlies · April 2nd, 2009, 11:55 AM

no no errors in the code, like i said it works perfectly well at college. if i double click on the form it goes to form load and i set a breakpoint and it goes to the procedure on loading, but the code stops on opening the connection, it never goes to the msgbox or to the sql on the form load