如何将一个列表框中的项的总和相乘？

因此，我正在编写一个程序，您可以在其中从组合框中选择产品，选择数量，然后它将在列表框中返回价格和数量。

但是，我希望能够将每行产品的价格乘以数量，然后将所有行的成本相加得出“总成本”。我该怎么做？

形式如下：

TL; DR如何将每条产品的价格相乘，然后将每条产品的总价格相加。谢谢你！！

这是我的代码：IGNORE OLEDB部件-有些命名不正确，因为它是WIP

Imports System.Data.OleDb
Public Class frmOrderProduct
    Dim iPadCasePrice As String
    Dim iPad2Price As String
    Dim prod_list As List(Of String)

    Private Sub frmOrderProduct_Load(sender As Object, e As EventArgs) Handles MyBase.Load

        cmboxProduct.Items.Add("iPad Case")
        cmboxProduct.Items.Add("iPad 2")

        iPadCasePrice = "$20.00"
        iPad2Price = "$200.00"


        txtUsername.Text = frmLogin.txtUsername.Text

    End Sub

    Private Sub btnAddToCart_Click(sender As Object, e As EventArgs) Handles btnAddToCart.Click

        If cmboxProduct.SelectedItem = "" Or txtQuantity.Text = "" Then
            MsgBox("Please fill out all required fields", MsgBoxStyle.OkOnly, "Invalid entered data")
        Else
            ListBoxCart.Items.Add("x" & txtQuantity.Text & " " & cmboxProduct.SelectedItem & " " & txtPriceEach.Text)

            'txtShoppingCart.AppendText("x" & txtQuantity.Text & " " & Product1 & Environment.NewLine)
        End If
    End Sub

    Private Sub txtQuantity_KeyPress(ByVal sender As Object, ByVal e As KeyPressEventArgs) Handles txtQuantity.KeyPress

        If Asc(e.KeyChar) <> 8 Then
            If Asc(e.KeyChar) < 48 Or Asc(e.KeyChar) > 57 Then
                e.Handled = True
            End If
        End If

    End Sub

    Private Sub btnOrderProducts_Click(sender As Object, e As EventArgs) Handles btnOrderProducts.Click

        Dim numberOfItems = ListBoxCart.Items.Count
        For Each item As String In ListBoxCart.Items

            Try

                cm = New OleDbCommand
                With cm
                    .Connection = cn
                    .CommandType = CommandType.Text
                    .CommandText = "INSERT INTO tblOrders ([ProductName],[Quantity],[PriceEach],[TotalPrice],[Username]) VALUES (@ProductName,@Quantity,@PriceEach,@TotalPrice,@Username)"

                    prod_list = item.Split(" ").ToList
                    Dim prod_name = prod_list.ElementAt(1)
                    Dim prod_quantity = Integer.Parse(prod_list.ElementAt(0).Remove("x"))
                    Dim price_each = prod_list.ElementAt(2)

                    .Parameters.Add(New OleDbParameter("@ProductName", OleDbType.VarChar, 255, prod_name))
                    .Parameters.Add(New OleDbParameter("@Quantity", OleDbType.VarChar, 255, prod_quantity))
                    .Parameters.Add(New OleDbParameter("@PriceEach", OleDbType.VarChar, 255, price_each))
                    .Parameters.Add(New OleDbParameter("@TotalPrice", OleDbType.VarChar, 255, price_each))
                    .Parameters.Add(New OleDbParameter("@Username", OleDbType.VarChar, 255, txtUsername.Text))
                    prod_list = New List(Of String)

                    cm.Parameters("@ProductName").Value = prod_name
                    cm.Parameters("@Quanity").Value = prod_quantity
                    cm.Parameters("@PriceEach").Value = price_each
                    cm.Parameters("@TotalPrice").Value =
                    cm.Parameters("@Username").Value = txtUsername.Text

                    cm.ExecuteNonQuery()
                    MsgBox("Record saved.", MsgBoxStyle.Information)
                    cmboxProduct.SelectedItem = ""
                    txtQuantity.Text = ListBoxCart.Text = ""

                    Exit Sub
                End With
            Catch ex As Exception
                MsgBox(ex.Message, MsgBoxStyle.Critical)
            End Try

        Next

    End Sub

    Private Sub btnClearCart_Click(sender As Object, e As EventArgs) Handles btnClearCart.Click

        ListBoxCart.Items.Clear()

    End Sub

    Private Sub cmboxProduct_SelectedIndexChanged(sender As Object, e As EventArgs) Handles cmboxProduct.SelectedIndexChanged

        If cmboxProduct.SelectedItem = "iPad Case" Then
            txtPriceEach.Text = iPadCasePrice
        End If

        If cmboxProduct.SelectedItem = "iPad 2" Then
            txtPriceEach.Text = iPad2Price
        End If

    End Sub
End Class