Login page with *******

Imports System.Net, Microsoft.Win32
Imports System.Management
Imports System****
Imports System.Security.Cryptography
Imports System.Text
Imports System.Threading
Dim username As String
Dim all As String
Dim logins As String = 0
Private Sub LoginButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles LoginButton.Click
Dim Name As String = True

logins = logins + 1
If logins = 4 Then
MsgBox("You have failed 3 times!")
Application.Exit()
Exit Sub
End If

Dim web As New WebClient() Dim i As String = textbox1.Text & ":" & textbox2.Text

Dim response As String = web.DownloadString("YOUR ******* ACCOUNT.txt")
If response.Contains(i) Then
Else : MsgBox("Invalid Login", MsgBoxStyle.Information)
Exit Sub
End If
If textbox1.Text = "" Or textbox2.Text = "" Then
MsgBox(" Error ")
Else
MsgBox("Welcome Member : " + textbox1.Text)
Me.Hide()

End If

End Sub

It is based on a single user name and I want to add more than one user in txt file

Dim response As String = web.DownloadString("YOUR ******* ACCOUNT.txt")
If response.Contains(i) Then

Dim username As String
Dim loginAttempts As Integer= 0

Private Sub LoginButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles LoginButton.Click
If textbox1.Text = "" Or textbox2.Text = "" Then
MsgBox("Username/Password Error ") '' textBox1.Focus() or textBox2.Focus() ?
Exit Sub
End If

loginAttempts += 1
If logins = 4 Then
MsgBox("You have failed 3 times!")
Application.Exit()
End If

Dim web As New WebClient()
Dim userAccount As String = textbox1.Text & ":" & textbox2.Text

Dim response As String = web.DownloadString("YOUR ******* ACCOUNT.txt")
If response.Contains(userAccount) Then
''User/pass was found. Success.
loginAttempts = 0
username = textbox1.Text
MsgBox("Welcome Member : " + username)
Me.Hide()
Else
''User/pass not found.
MsgBox("Invalid Login", MsgBoxStyle.Information)
Exit Sub
End If

End Sub