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Login code for Visual Basic 2005 Beginners
Posted Date: 23 Mar 2008 Resource Type: Articles/Knowledge Sharing Category: Computer & Technology
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Posted By: Olufemi Member Level: Diamond
Rating:  Points: 5
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This code below will avail the VB2005 the opportunity to user a login form as security for a simple program. This example is design with MS Access as the database machine at the back end. With this codes the developer can control access to the system using the access table as the store for authorized users of the newly designed software.
With this simple blocks of code you can modify it to suit your purpose.
' 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
I have used it and it is perfectly running. In case you have any question don't hesitate to ask me.
Olufemi
Nigeria
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