This FAQ will explain how to show and close a login form correctly in .NET. It will not show how to do good login form code such as limiting login tries or how to connect to a db etc. The attached project was created with VS.NET 03. If you have 02, just create a new solution and project and add the form and module files.
There are two main points of interest in the project. frmLogin is the form class that encapsulates the login code. modMain shows how to use the class.
Code:
Public Enum LoginStatusENUM
LoginOk
LoginFailed
End Enum
Public Event LoginStatus(ByVal Status As LoginStatusENUM)
Private Sub TryLogin()
'This code should be replaced with good login code.
If txtName.Text = "John" And txtPassword.Text = "john" Then
Me.Close()
'Login was ok so raise the event with a login ok status
RaiseEvent LoginStatus(LoginStatusENUM.LoginOk)
Else
MessageBox.Show("Invalid Login")
End If
End Sub
Private Sub btnLogin_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnLogin.Click
TryLogin() 'Execute the login code to check user and password
End Sub
Private Sub btnCancel_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCancel.Click
'User canceled, close form and throw the event with a failed status
Me.Close()
RaiseEvent LoginStatus(LoginStatusENUM.LoginFailed)
End Sub
and the code from the module
Code:
Public Sub main()
Dim frmLogMeIn As frmLogin
frmLogMeIn = New frmLogin
'add the handler for the event
AddHandler frmLogMeIn.LoginStatus, AddressOf MyLoginStatus
frmLogMeIn.ShowDialog()
End Sub
Public Sub MyLoginStatus(ByVal Status As frmLogin.LoginStatusENUM)
'The user either canceled or loged in OK
If Status = frmLogin.LoginStatusENUM.LoginOk Then
'frmMain.ShowDialog()
MessageBox.Show("Showing Form Main!")
End If
'else login failed so drop out the back of the sub to close the program
End Sub
The code is commented well, but I'll give a quick overview of the code. For the login form, we handle all code to see if the user loged in OK or not. We raise the event when the login status has been decided. The form gets closed either way to allow full control to pass back to the event that handles the login status. If the MyLoginStatus sub doesn't open a form modally, then the app ends.
John Spano
President
NeoTekSystems, Inc.
www.NeoTekSystems.com
MCSD, MCTS-Windows, MCTS-Web, MCPD-Distributed, MCITP-SQLDev, MCITP-SQLAdmin