Public Class Form1

#Region " Windows Form Designer generated code "

#End Region

    Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Try
            Dim ConnStr As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source = F:\Rahul\Teaching\Northwind.mdb"
            Dim ObjConn As New OleDb.OleDbConnection(ConnStr)
            Dim dt As New DataTable
            Dim SqlStr As String = "Select OrderID as ID from Orders"
            Dim ObjCmmd As New OleDb.OleDbCommand(SqlStr, ObjConn)
            Dim ObjDA As New OleDb.OleDbDataAdapter(ObjCmmd)
            ObjDA.Fill(dt)

            Dim i As Integer
            For i = 0 To dt.Rows.Count - 1
                ComboBox1.Items.Add(dt.Rows(i)(0))
            Next
        Catch ex As Exception
            MessageBox.Show("Exception: " + ex.Message)
        End Try
    End Sub

    Private Sub btnCalculate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCalculate.Click
        Try
            Dim ConnStr As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source = F:\Rahul\Teaching\Northwind.mdb"
            Dim ObjConn As New OleDb.OleDbConnection(ConnStr)
            Dim dt As New DataTable
            Dim SqlStr As String = "Select count(*), sum(UnitPrice * Quantity) from [order details] where orderid="
            SqlStr += Convert.ToString(ComboBox1.SelectedItem)
            Dim ObjCmmd As New OleDb.OleDbCommand(SqlStr, ObjConn)
            Dim ObjDA As New OleDb.OleDbDataAdapter(ObjCmmd)
            ObjDA.Fill(dt)

            Dim PreTotal As Double = dt.Rows(0)(1)
            Dim NItems As Integer = dt.Rows(0)(0)
            Dim Discount As Double = 0
            Dim Shipping As Double = 0
            Dim OrderTotal As Double = 0
            Shipping = 0.1 * PreTotal
            If (NItems >= 3 And NItems < 5) Then
                Discount = 0.1 * PreTotal
            ElseIf (NItems >= 5) Then
                Discount = 0.15 * PreTotal
                Shipping = 0
            End If
            OrderTotal = PreTotal - Discount + Shipping

            lblPreTotal.Text = FormatCurrency(PreTotal)
            lblDiscount.Text = FormatCurrency(Discount)
            lblShipping.Text = FormatCurrency(Shipping)
            lblOrderTotal.Text = FormatCurrency(OrderTotal)

        Catch ex As Exception
            MessageBox.Show("Exception: " + ex.Message)
        End Try
    End Sub
End Class