(VB) สอบถาม Code โปรแกรม คำนวณโปรโมชั่นของราคาสินค้า

Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim product_code As String
        Dim price As Decimal
        Dim dis As Decimal
        Dim total As Decimal

If IsNumeric(TextBox1.Text) Then
            price = TextBox1.Text
 product_code = DropDownList1.SelectedValue
            dis = Calculate(product_code, price)

            total = price - dis
            TextBox2.Text = ("" & price)
            TextBox3.Text = (" " & dis)
            TextBox4.Text = (" " & total)
        Else
        End If
    End Sub


Function Calculate(ByVal product_code As String, ByVal price As Decimal) As Decimal
        Dim dis As Decimal = 0

        For Each dr As DataRow In dt.Rows
            If (dr.Item("Product") = product_code) Then

                If price >= dr.Item("min_p") And price <= dr.Item("max_p") Then
                    dis = dr.Item("dis")

                End If
            End If

        Next

        Return dis
    End Function

Imports System.Data

Public Class WebForm1
    Inherits System.Web.UI.Page
    Dim dt As New DataTable
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        dt.Columns.Add("promotion_id", GetType(Integer))
        dt.Columns.Add("Product", GetType(String))
        dt.Columns.Add("min_p", GetType(Decimal))
        dt.Columns.Add("max_p", GetType(Decimal))
        dt.Columns.Add("dis", GetType(Decimal))

        ' Start A1001
        Dim drA1 As DataRow = dt.NewRow
        drA1.Item("promotion_id") = 1
        drA1.Item("Product") = "A1001"
        drA1.Item("min_p") = 0
        drA1.Item("max_p") = 499.99
        drA1.Item("dis") = 0
        dt.Rows.Add(drA1)

        Dim drA2 As DataRow = dt.NewRow
        drA2.Item("promotion_id") = 2
        drA2.Item("Product") = "A1001"
        drA2.Item("min_p") = 500
        drA2.Item("max_p") = 999.99
        drA2.Item("dis") = 300
        dt.Rows.Add(drA2)

        Dim drA3 As DataRow = dt.NewRow
        drA3.Item("promotion_id") = 3
        drA3.Item("Product") = "A1001"
        drA3.Item("min_p") = 1000
        drA3.Item("max_p") = DBNull.Value
        drA3.Item("dis") = 500
        dt.Rows.Add(drA3)
        ' End A1001

        ' Start B1001
        Dim drB1 As DataRow = dt.NewRow
        drB1.Item("promotion_id") = 1
        drB1.Item("Product") = "B1001"
        drB1.Item("min_p") = 0
        drB1.Item("max_p") = 999.99
        drB1.Item("dis") = 500
        dt.Rows.Add(drB1)

        Dim drB2 As DataRow = dt.NewRow
        drB2.Item("promotion_id") = 2
        drB2.Item("Product") = "B1001"
        drB2.Item("min_p") = 1000
        drB2.Item("max_p") = 4999.99
        drB2.Item("dis") = 1000
        dt.Rows.Add(drB2)

        Dim drB3 As DataRow = dt.NewRow
        drB3.Item("promotion_id") = 3
        drB3.Item("Product") = "B1001"
        drB3.Item("min_p") = 5000
        drB3.Item("max_p") = DBNull.Value
        drB3.Item("dis") = 1500
        dt.Rows.Add(drB3)
        ' End B1001

        ' Start C1001
        Dim drC1 As DataRow = dt.NewRow
        drC1.Item("promotion_id") = 1
        drC1.Item("Product") = "C1001"
        drC1.Item("min_p") = 0
        drC1.Item("max_p") = 1499.99
        drC1.Item("dis") = 500
        dt.Rows.Add(drC1)


        Dim drC2 As DataRow = dt.NewRow
        drC2.Item("promotion_id") = 2
        drC2.Item("Product") = "C1001"
        drC2.Item("min_p") = 1500
        drC2.Item("max_p") = 2999.99
        drC2.Item("dis") = 1000
        dt.Rows.Add(drC2)

        Dim drC3 As DataRow = dt.NewRow
        drC3.Item("promotion_id") = 3
        drC3.Item("Product") = "C1001"
        drC3.Item("min_p") = 3000
        drC3.Item("max_p") = 5999.99
        drC3.Item("dis") = 1500
        dt.Rows.Add(drC3)

        Dim drC4 As DataRow = dt.NewRow
        drC4.Item("promotion_id") = 4
        drC4.Item("Product") = "C1001"
        drC4.Item("min_p") = 6000
        drC4.Item("max_p") = DBNull.Value
        drC4.Item("dis") = 3000
        dt.Rows.Add(drC4)
        ' End C1001
        '------------------
        GridView1.DataSource = dt
        GridView1.DataBind()
        ' -------------------

    End Sub


    Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim product_code As String
        Dim price As Decimal
        Dim dis As Decimal
        Dim total As Decimal
        Dim num As Decimal
        Dim sum As Decimal

        If IsNumeric(TextBox1.Text) Then
            price = TextBox1.Text
            price = (Math.Truncate(price * 100)) / 100
            product_code = DropDownList1.SelectedValue

            dis = Calculate(product_code, price)
            num = TextBox5.Text
            sum = price * num
            total = price - dis

            TextBox2.Text = ("" & price * num)
            TextBox3.Text = (" " & dis)
            TextBox4.Text = (" " & sum - dis)
        Else
        End If
    End Sub
    Function Calculate(ByVal product_code As String, ByVal price As Decimal) As Decimal
        Dim dis As Decimal = 0
        For Each dr As DataRow In dt.Rows

            If (dr.Item("Product") = product_code) Then
                If Not dr.Item("max_p").GetType = GetType(Decimal) Then
                    If price >= dr.Item("min_p") Then
                        dis = dr.Item("dis")
                    End If
                Else
                    If price >= dr.Item("min_p") And price <= dr.Item("max_p") Then
                        dis = dr.Item("dis")
                    End If
                End If
            End If
        Next

        Return dis
    End Function


    Protected Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles TextBox1.TextChanged

    End Sub
End Class