Sistema de Login

Tela de Login

Imports System.Data

Imports System.Data.OleDb

Public Class frmLogin

    Public Function validaCampos() As Boolean

        If txtLogin.Text = "" Then

            MsgBox("Preencha o campo login.", MsgBoxStyle.Critical)

            txtLogin.Focus()

            Return False

        End If

        If txtSenha.Text = "" Then

            MsgBox("Preencha o campo senha.", MsgBoxStyle.Critical)

            txtSenha.Focus()

            Return False

        End If

        Return True

    End Function

    Private Sub PAcessarSistema()

        Dim dr As OleDbDataReader = Nothing

        Using con As OleDbConnection = GetConnection()

            Try

                con.Open()

                Dim sql As String = "SELECT * FROM usuarios WHERE login=? and senha=?"

                Dim cmd As OleDbCommand = New OleDbCommand(sql, con)

                cmd.Parameters.Add(New OleDb.OleDbParameter("@login", txtLogin.Text))

                cmd.Parameters.Add(New OleDb.OleDbParameter("@senha", txtSenha.Text))

                dr = cmd.ExecuteReader(CommandBehavior.SingleRow)

                If dr.HasRows Then

                    dr.Read()

                    strLogin = dr.Item("Login")

                    strPerfil = dr.Item("perfil")

                    Me.Dispose()

                    frmPrincipal.Show()

                Else

                    MsgBox("Dados inválidos. Por favor tente novamente.", MsgBoxStyle.Critical)

                    txtLogin.Text = ""

                    txtSenha.Text = ""

                    txtLogin.Focus()

                End If

            Catch ex As Exception              

            Finally

                dr.Close()

                con.Close()

            End Try

        End Using

    End Sub

    Private Sub btnLogar_Click(sender As Object, e As EventArgs) Handles btnLogar.Click

        If validaCampos() = False Then Exit Sub

        PAcessarSistema()

    End Sub

    Private Sub btnCancelar_Click(sender As Object, e As EventArgs) Handles btnCancelar.Click

        intPergunta = MsgBox("Tem certeza que deseja encerrar a aplicação?", MsgBoxStyle.Question + MsgBoxStyle.YesNo)

        If intPergunta <> vbYes Then Exit Sub

        End

    End Sub

End Class

Tela Principal

Public Class frmPrincipal

    Private Sub frmPrincipal_Load(sender As Object, e As EventArgs) Handles MyBase.Load

        lblLogin.Text = strLogin

        lblPerfil.Text = strPerfil

    End Sub

End Class

Código do Módulo

Imports System.Data

Imports System.Data.OleDb

Module mdlAcesso

    Public strLogin As String

    Public strPerfil As String

    Public intPergunta As Integer

    Public Function GetConnection() As OleDbConnection

        Dim strConnection As String = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=E:\Projetos Visual Studio 2012\SistemaLogin\sistema.accdb"

        Return New OleDbConnection(strConnection)

    End Function

End Module

Espero ter ajudado, abraços.