I want to creat login form with user access level i.e. i want to check if user is admin or employee.

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VB

SQL-Server-2012

Private Sub loginbtn_Click_1(sender As System.Object, e As System.EventArgs) Handles loginbtn.Click
        For Each ctrl As Control In Me.Controls
            If (usernametxt.Text & passwordtxt.Text = String.Empty) Then
                ErrorProvider1.SetError(usernametxt, "Incorrect")
                ErrorProvider2.SetError(passwordtxt, "Incorrect")
                MsgBox("Fill The Details", MsgBoxStyle.Exclamation)
                Exit Sub
            End If
        Next
        con.Open()
        l = "Select username, password, type From Login where username='" & usernametxt.Text & "' and password='" & passwordtxt.Text & "'"
        com = New SqlCommand(l, con)
        dr = com.ExecuteReader
        dr.Read()
        If usernametxt.Text = dr.GetString(0) Then
            If passwordtxt.Text = dr.GetString(1) Then
                If dr.GetString(2) = "ADMIN" Then
                    Me.Hide()
                    HomePage.Show()
                ElseIf dr.GetString(2) = "EMPLOYEE" Then
                    Me.Hide()
                    HomePage.Show()
                    StudentReg.editbtn.Enabled = False
                    StudentReg.removebtn.Enabled = False
                    StaffReg.editbtn.Enabled = False
                    StaffReg.removebtn.Enabled = False
                    HomePage.CourseFeesToolStripMenuItem.Enabled = False
                    HomePage.BatchesToolStripMenuItem.Enabled = False
                    HomePage.EventsToolStripMenuItem.Enabled = False
                    Billing.Button1.Enabled = False
                    HomePage.ReportsToolStripMenuItem.Enabled = False
                End If
            End If
        Else
            MsgBox("Please Enter Correct Username And Password", MsgBoxStyle.Critical)
        End If
        usernametxt.Text = ""
        passwordtxt.Text = ""
        con.Close()
    End Sub

What I have tried:

I have create Login Form and Database in SQL Server. The database has table Login with 3 columns username, password, type. If type = ADMIN then he have access to full application but if type = employee then some buttons on other form get disable. At first time the code is working when admin or employee gets logged in. i.e. When employee gets logged and open a form the buttons get disable but when he closes and opens the same form again the buttons get enabled. I tried many things but I have not be able solve the problem. Help me with some solution. I want the buttons should be disable throughout the time when employee is logged in to application.