visual basic.net login form code

' Place this code under your Public Class. If your form name is Login, then place it under Public Class Login
Inherits System.Windows.Forms.Form
Dim iCount As Integer ' this integer is declared to help count the number of imes a user tried to login.
Dim frmMain As New MainScreen ' this line declares a variable that will point the user to the Main Screen upon a successful login. The second form created is called MainScreen.vb
Private Sub btnLogin_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnLogin.Click
'The connection string is used to describe the type of database, the security information and the location to the database.
Dim ConString As String = "Provider=Microsoft.Jet.OLEDB.4.0;Password="""";User ID=Admin;Data Source=""databasename.mdb"";"
'Create a new connection object and assign the ConString Connection String above
Dim DBCon As New OleDb.OleDbConnection(ConString)
' g_login is a global variable defined in a Module that captures the login name and passes it from form to form. To create this, just create a Module, say Module1.vb and in it put "Public g_login as String" {g meaning global and login to represent the global login}
g_login = Me.txtUsername.Text

Dim strPassword As String = Me.txtPassword.Text

If g_login = "" Or strPassword = "" Then
MessageBox.Show("You are missing information. Please make sure that both the username and password fields are filled out.", "Missing Info")
Me.txtUsername.Focus()
Return
End If
' The database has two fields in the Users table. A UserID field, which is the primary key and declared as a text. The other field is Password, which is a text as well.
Dim strsql As String = "SELECT [UserID], [Password] FROM Users WHERE [UserID]='" & g_login & "' "

Dim cm As New OleDb.OleDbCommand(strsql, DBCon)
Dim dr As OleDb.OleDbDataReader
Dim valid As Boolean = False
Dim HasRows As Boolean = False
Try
DBCon.Open()
dr = cm.ExecuteReader
If dr.HasRows Then
While dr.Read
If strPassword = dr.Item("Password") Then
valid = True
End If
End While
HasRows = True
End If
dr.Close()
Catch exO As OleDb.OleDbException
MessageBox.Show(exO.Message)
Catch ex As Exception
MessageBox.Show(ex.Message)
Finally
If DBCon.State = ConnectionState.Open Then
DBCon.Close()
End If
cm = Nothing
dr = Nothing
DBCon.Dispose()
GC.Collect()
End Try
iCount = iCount + 1
If valid = True Then
Me.Hide()
frmMain.Show()
ElseIf iCount = 3 Then
MessageBox.Show("Contact Safreak!", "Invalid Info")
Me.Close()
ElseIf HasRows = False Then
MessageBox.Show("Invalid user name, try again!", "Invalid Info")
Me.txtUsername.Focus()
Me.txtUsername.Text = ""
Me.txtPassword.Text = ""
Else
MessageBox.Show("Invalid password, try again!", "Invalid Info")
Me.txtPassword.Focus()
Me.txtPassword.Text = ""
End If

End Sub