Close form from second form - vb.net

Question

My first form is login form, when user correctly log in i am hiding login form and showing up second form. Now instead of hiding login form i want to close it from second form. I thought i will be able to do it but somehow i got troubles with it.
So far i did like this below.
I made interface which my FrmLogin implements:
Public Class FrmLogin
Implements ICloseLogin
Interface:
Public Interface ICloseLogin
Sub Close()
End Interface
FrmLogin implementing interface:
Private Sub ICloseLogin_Close() Implements ICloseLogin.Close
Me.Close()
End Sub
Now i am passing FrmLogin (Me) to second form constructor:
Private Sub ShowMainForm()
Dim FrmMain As New FrmMainMDI(Me)
FrmMain.IsMdiContainer = True
FrmMain.StartPosition = FormStartPosition.CenterScreen
FrmMain.Show()
'Me.Hide() 'not anymore
End Sub
Second form:
Public Class FrmMainMDI
Private closeloginfform As ICloseLogin
Sub New(frmlogin As ICloseLogin)
' This call is required by the designer.
InitializeComponent()
' Add any initialization after the InitializeComponent() call.
closeloginfform = frmlogin
End Sub
Private Sub FrmMainMDI_Shown(sender As Object, e As EventArgs) Handles MyBase.Shown
closeloginfform.Close()
End Sub
and when i debug and when it comes to line: closeloginfform.Close() i suppose to see only FrmLogin to be closed, but all is closing somehow. Why?
For further discussion:
Imports DataAccessLayer
Imports FormsUtils
Imports BusinessLayer
Imports System.Data.SqlClient
Imports System.Configuration
Imports System.Reflection
Imports System.IO
Imports Microsoft.WindowsAPICodePack.Dialogs
Imports Probix
Public Class FrmLogin
Private Property Form As New FormUtils
Private Property DB As New Procs
Private Property _login As String
Private Property _password As String
Private Sub btnLogin_Click(sender As System.Object, e As System.EventArgs) Handles btnLogin.Click
CheckAccess()
End Sub
Private Sub btnClose_Click(sender As System.Object, e As System.EventArgs) Handles btnClose.Click
Me.Close()
End Sub
Private Sub FrmLogin_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
Try
DB.OpenConn()
If DB.conn.State = ConnectionState.Open Then
Call Form.InitCombo(CboLogin, "SELECT * from tbLogin", DB.conn, "Login", "Login")
Call Form.InitCombo(CboLanguage, "SELECT * from tbLanguage where Active = 1", DB.conn, "Language", "Id")
Lang.name = DirectCast([Enum].Parse(GetType(Lang.LangShortcut), CboLanguage.GetItemText(CboLanguage.SelectedItem)), Lang.LangShortcut)
Else
Logger.LogIt(Modules.FrmLogin.ToString & ": " & Methods.FrmLogin_Load.ToString, WriteMsg.Write(IssueCode.SqlServerConnectionError_pl), Application.StartupPath & "\log.txt", False)
Application.Exit()
End If
Catch ex As Exception
Logger.LogIt(ex.tostring)
Application.Exit()
Finally
DB.CloseConn()
End Try
End Sub
Private Sub CheckAccess()
Try
_login = CboLogin.SelectedValue
_password = txtPassword.Text
If Not String.IsNullOrEmpty(txtPassword.Text) And Form.WybranoCombo(CboLogin, "Zaznacz login") Then
Dim strcon = New AppSettingsReader().GetValue("ConnectionString", GetType(System.String)).ToString()
Using con As New SqlConnection(strcon)
Using cmd As New SqlCommand("Select COUNT(*) FROM tbLogin WHERE Login = #Login And Password = #Password", con)
cmd.CommandType = CommandType.Text
cmd.Parameters.AddWithValue("#Login", _login)
cmd.Parameters.AddWithValue("#Password", _password)
con.Open()
Dim o As Integer = cmd.ExecuteScalar()
'--CREDENTIALS OK
If o > 0 Then
CboLogin.Hide()
txtPassword.Hide()
btnLogin.Hide()
Label1.Hide()
Label2.Hide()
Try
Catch ex As Exception
MsgBox(ex.ToString)
End
End Try
'--CREDENTIALS NOT OK !!
Else
MsgBox("Wrong credentials")
End If
End Using
End Using
Else
MsgBox("Write some password !!")
End If
Catch ex As Exception
Logger.LogIt(Modules.FrmLogin.ToString & ":" & Methods.FrmLogin_Load.ToString, WriteMsg.Write(IssueCode.Unknown_pl) & " ------> EX-MESSAGE: " & ex.ToString, Application.StartupPath & " \log.txt", False)
Return
End Try
End Sub
Public Sub taskDialog_Opened(sender As Object, e As EventArgs)
Dim taskDialog As TaskDialog = TryCast(sender, TaskDialog)
taskDialog.Icon = taskDialog.Icon
If Not taskDialog.FooterIcon = TaskDialogStandardIcon.None Then
taskDialog.FooterIcon = taskDialog.FooterIcon
End If
taskDialog.InstructionText = taskDialog.InstructionText
End Sub
End Class
Module Program:
Module Program
Public Sub main()
Application.EnableVisualStyles()
Dim result As DialogResult
Using frmL As New FrmLogin
result = frmL.ShowDialog
End Using
If result = DialogResult.OK Then
Dim FrmMainMDI As New FrmMainMDI()
Application.Run(FrmMain)
End If
End Sub
End Module
Further discussion 2
Solved???: I've added line within CheckAccess() sub, this line:
Me.DialogResult = DialogResult.OK
so this peace of code has been changed only:
...
'--CREDENTIALS OK
If o > 0 Then
CboLogin.Hide()
txtPassword.Hide()
btnLogin.Hide()
Label1.Hide()
Label2.Hide()
Try
'*************************************
Me.DialogResult = DialogResult.OK '<=========================================
'*************************************
Catch ex As Exception
MsgBox(ex.ToString)
End
End Try
'--CREDENTIALS NOT OK !!
Else
MsgBox("Wrong credentials")
End If
...

Answer 1

A less involved way to do this is to start your app from Sub Main and only start the app if the LogIn is correct. For this:
Add a module to your App, and name it Program. Add a Public Sub Main to it
Go to Project Properties and Uncheck Enable Application Framework
Now, for the Startup Object, select "Sub Main"
You can actually name the module anything, "Program" is descriptive and the convention used in C#. Then the Sub Main code:
Public Sub Main()
Application.EnableVisualStyles()
Dim result As DialogResult
Using frmL As New frmLogin
result = frmL.ShowDialog
End Using
If result = DialogResult.OK Then
frmMain = New MainFrm()
Application.Run(frmMain)
End If
End Sub
Now, your two forms don't even have to know about each other. The MainForm will not even exist if/when the login fails. Whatever overhead there is related to starting/Loading the MainForm is also delayed until (and unless) the log in passes.
Your login button would be something like this (depending on how many failed attempts are allowed):
Private Sub btnLogIn_Click(sender As Object, e As EventArgs) Handles btnLogIn.Click
If IsValidUser(tbName.Text, tbPW.Text) Then
DialogResult = Windows.Forms.DialogResult.OK
Else
If tries >= 3 Then
DialogResult = Windows.Forms.DialogResult.Cancel
Else
tries += 1
Exit Sub
End If
End If
Me.Hide()
End Sub