Windows Forms: LoginForm and MainForm

Question

Currently, I have a LoginForm that authenticates a user and it works fine. I have a MainForm, which is displayed if a valid username and password is entered. I have done this by using the following code in my LoginForm:

Private Sub OK_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles OK.Click
    Dim ValidUser As Boolean

    // Authentication code in which I set ValidUser to either True or False

    If ValidUser Then
      Dim mainForm As MainForm = New MainForm()
      mainForm.Show()
      Me.Hide()
    End If
End Sub

Now this does exactly what I want except I fear it's a work around and it's not the best approach. Also, note that I am using Me.Hide() to hide the LoginForm, is there a way to show the MainForm and then close the LoginForm instead of hiding it? Doesn't Me.Hide() call creates an overhead?

Thanks in advance.

Answer 1

If you get a dozen replies I bet you get a dozen methods.  None of them are really workarounds, although I would not recommend making your Login Form and the Application's Main Form (not the same as your class named MainForm) be the same Form.

Click Project -> Properties and select the Application Tab and click Application Events.  Instructions how to use Application Events are found there.

My recommendation is to make your MainForm class be the Main Form in the application, then display the Login Form as a modal dialog box from Application.StartUp.  As part of your checking in the LoginForm, make its own DialogResult return OK if the user authenticates and CANCEL if the user does not authenticate.

At that point you can kill the application in its own startup routine a number of ways.  My recommendation is to make an Application Scoped Boolean value indicating whether the application should kill or not, and then use the Load Event in whatever form is set as the Application Main Form to check that Boolean; this way you can make the MainForm close itself (application terminate) or simply disable all its own controls and redisplay the Login Form based on the switch value.

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It never hurts to try. In a worst case scenario, you'll learn from it.

Answer 2

Do you wish to have the main form be visible in the background while your login form authenticates the user, or do you want to only show the login form and then show the mail form once the user is authenticated?

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Matt Kleinwaks - MSMVP MSDN Forums Moderator - www.zerosandtheone.com

Answer 3

I would prefer to show ONLY the login form first and if the user is authenticated, then show main form.

 

Answer 4

I would prefer to show ONLY the login form first and if the user is authenticated, then show main form.

In Application Events:

 

Friend Authenticated As System.Boolean = False

Private Sub Application_Startup( _ 
ByVal sender As System.Object, _
ByVal e As Microsoft.VisualBasic.ApplicationServices.StartupEventArgs) _
Handles Me.Startup

Dim MyLoginForm As New LoginForm
'Only changes Authenticated to TRUE if the Form returns OK
If MyLoginForm.ShowDialog = DialogResult.OK Then
Me.Authenticated = True
End If

End Sub

 

In MyLoginForm, ButtonClick Event:

 

'Do your authentication-fu
If AuthenticationAlgorithmBoolean = True Then
Me.DialogResult = DialogResult.OK
Else
Me.DialogResult = DialogResult.Cancel
End If

Me.Close

 

In MainForm.Load Event:

 

If My.Application.Authenticated = False Then
Me.Close
End If

 

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It never hurts to try. In a worst case scenario, you'll learn from it.

Answer 5

I think I know what you are saying but would you be able to provide some sample code for me to see? Just to clear a few things up.

Thanks again.

Answer 6

I think I know what you are saying but would you be able to provide some sample code for me to see? Just to clear a few things up.

Thanks again.

I don't have the faintest idea what more I can do for you.  All you have to do is copy/paste into the right places, and I told you what the right places are too.

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It never hurts to try. In a worst case scenario, you'll learn from it.

Answer 7

Thanks Andrew, I appreciate all your help.