Hi guys i am a total beginner on VB.As mention on the tittle i would love a help on my problem.Here is my code

Imports System
Imports System.Data
Imports System.Data.OleDb
Imports System.Data.SqlClient

Public Class Form1

Dim conn As New System.Data.OleDb.OleDbConnection()


Private Sub btnSignUp_Click(sender As Object, e As EventArgs) Handles btnSignUp.Click
    Me.Hide()
    Form2.Show()
End Sub

Private Sub btnExit_Click(sender As Object, e As EventArgs) Handles btnExit.Click
    Me.Close()
End Sub

Private Sub btnSignIn_Click(sender As Object, e As EventArgs) Handles btnSignIn.Click


    Dim sql As String = "SELECT * FROM table WHERE Username='" & UsernameTextBox.Text & "' AND Password = '" & PassTextBox.Text & "'"
    Dim sqlCom As New System.Data.OleDb.OleDbCommand(sql)


    Dim sqlRead As System.Data.OleDb.OleDbDataReader = sqlCom.ExecuteReader()

    If sqlRead.Read() Then
        Form3.Show()
        Me.Hide()

    Else
        ' If user enter wrong username and password combination
        ' Throw an error message
        MessageBox.Show("Username and Password do not match..", "Authentication Failure", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)

        'Clear all fields
        PassTextBox.Text = ""
        UsernameTextBox.Text = ""

        'Focus on Username field
        UsernameTextBox.Focus()
    End If

End Sub

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles Me.Load
    conn.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\ser\Desktop\test.accdb"
    If conn.State = ConnectionState.Closed Then
        MsgBox("OPEN")
    Else
        MsgBox("CLOSE")
    End If

End Sub

End Class

You have to open the connection before you read. Here's an example

lvwResults.Items.Clear()

Dim con As New OleDbConnection("Provider=SQLNCLI10;Server=.\SQLEXPRESS;Database=PUBS;Trusted_Connection=Yes;Connect Timeout=15;")
Dim cmd As New OleDbCommand("", con)

cmd.CommandText = "SELECT au_lname,au_fname,phone " _
                & "  FROM authors                 " _
                & " WHERE au_lname like ?         " _
                & "   AND phone    like ?         " _
                & " ORDER BY au_lname             "

cmd.Parameters.AddWithValue("@lastName", txtLastName.Text)
cmd.Parameters.AddWithValue("@phone   ", txtPhone.Text)

con.Open()
Dim rdr As OleDbDataReader = cmd.ExecuteReader()

Do While rdr.Read
    lvwResults.Items.Add(New ListViewItem({rdr("au_lname"), rdr("au_fname"), rdr("phone")}))
Loop

rdr.Close()
con.Close()

Hi,

Also you need to specify that your command will use the connection...

That was supplied as the second parameter in the declaration

Dim cmd As New OleDbCommand("", con)