VB.net ByVal and ByRef doesnt work - vb.net

Question

So i have a couple of subs and i want to share variables between them... I'm new to programming and i don't understand how to use ByVal and ByRef. I'm trying to make a login page.
Public Class Form1
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles LoginButton.Click (ByRef BlnCorrectPassword As Boolean, ByRef BlnCorrectLogin As Boolean)
If blncorrectlogin = True And blncorrectpassword = True Then
MsgBox("This part is still being developed!") ' I will make this form close and open a new form.
Else
MsgBox("The login or password is incorrect, please try again.")
End If
End Sub
Private Sub Label1_Click(sender As Object, e As EventArgs)
End Sub
Private Sub Label1_Click_1(sender As Object, e As EventArgs) Handles Label1.Click
End Sub
Private Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles TextBox1.TextChanged
Dim BlnCorrectLogin As Boolean
If TextBox1.Text = "login" Then
BlnCorrectLogin = True
End If
End Sub
Private Sub TextBox2_TextChanged(sender As Object, e As EventArgs) Handles TextBox2.TextChanged
Dim BlnCorrectPassword As Boolean
If TextBox1.Text = "password" Then
BlnCorrectPassword = True
End If
End Sub
End Class

Answer 1

You can dramatically reduce the complexity if the username and password are checked in a sub and only check them on the button click event. You don't need to check if they're correct every time someone changes the values of the textboxes.
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles LoginButton.Click
If CheckLoginDetails() = True Then
MsgBox("This part is still being developed!") ' I will make this form close and open a new form.
Else
MsgBox("The login or password is incorrect, please try again.")
End If
End Sub
Private Function CheckLoginDetails() As Boolean
If TextBox1.Text = "login" AndAlso TextBox2.Text = "password" Then
Return True
Else
Return False
End If
End Function

Answer 2

if you want to use BlnCorrectPassword or BlnCorrectLogin with other Subs or Functions define them as global variables within that class as such
Public Class Form1
Private BlnCorrectPassword as Boolean = False
Private BlnCorrectLogin as Boolean = False
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles LoginButton.Click
If blncorrectlogin = True And blncorrectpassword = True Then
MsgBox("This part is still being developed!") ' I will make this form close and open a new form.
Else
MsgBox("The login or password is incorrect, please try again.")
End If
End Sub
Private Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles TextBox1.TextChanged
If TextBox1.Text = "login" Then
BlnCorrectLogin = True
End If
End Sub
Private Sub TextBox2_TextChanged(sender As Object, e As EventArgs) Handles TextBox2.TextChanged
If TextBox1.Text = "password" Then
BlnCorrectPassword = True
End If
End Sub
End Class
EDIT: also you do not have to check the entered Text with every letter (TextChanged) as long as you do not use it, so just check the entered text when you click the LoginButton, in that way you don't need boolean variables and have two less Subs

Answer 3

The code is still ugly and can definitely be simplified:
1.) blncorrectlogin = True And blncorrectpassword = True => You do not need to write = TRUE ; AND should not be used , use AndAlso.
2.) MsgBox is deprecated. Use MessageBox.Show instead.
3.) Textchanged can be concatenated. If like this:
If TextBox1.Text = "login" Then
BlnCorrectLogin = True
End If
are totally crap and senseless.
4.) Strings should not be compared with "=" , use .Equals for that.
Option Strict On 'Always write this
Option Infer Off 'Always write this
Imports System.IO
Public Class Form1
Private BlnCorrectPassword As Boolean = False
Private BlnCorrectLogin As Boolean = False
Private Sub TextBoxes_TextChanged(sender As Object, e As EventArgs) Handles TextBox1.TextChanged, TextBox2.TextChanged
If sender.Equals(TextBox1) Then
BlnCorrectLogin = TextBox1.Text.Equals("login")
End If
If sender.Equals(TextBox2) Then
BlnCorrectPassword = TextBox2.Text.Equals("password")
End If
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
If Not (BlnCorrectLogin AndAlso BlnCorrectPassword) Then
'do some stuff
MessageBox.Show("The login or password is incorrect, please try again.")
Exit Sub 'exit the sub
End If
'login data correct
MessageBox.Show("This part is still being developed!")
End Sub
End Class