Pertam bikin tabel user di database
bikin form Login
Username: Label dan TextBox: name txtUsername
Password: Label dan TextBox: name txtPassword, passwordChar isien (*)
Button Login

Private Sub OK_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles OK.Click
        Dim conn As MySqlConnection
        conn = New MySqlConnection
        conn.ConnectionString = "server=localhost; user id=root; password= ; database=program_rpl"
            Try
                conn.Open()
            Catch myerror As MySqlException
                MsgBox("Ada kesalahan dalam koneksi database")
            End Try
            Dim myAdapter As New MySqlDataAdapter

            Dim sqlquery = "SELECT * FROM userWHERE Username = '" + txtUsername.Text + "' AND Password= '" + txtPassword.Text + "'"
            Dim myCommand As New MySqlCommand
            myCommand.Connection = conn
            myCommand.CommandText = sqlquery

            myAdapter.SelectCommand = myCommand
            Dim myData As MySqlDataReader
            myData = myCommand.ExecuteReader()

            If myData.HasRows = 0 Then
                MsgBox("Username atau Password ada yang salah !", MsgBoxStyle.Exclamation, "Error Login")
            Else
            MsgBox("Login Berhasil, Selamat Datang " & UsernameTextBox.Text & " ! ", MsgBoxStyle.Information, "Successfull Login")
            Form1.Show()
            Me.Hide()
            End If
    End Sub