从Access数据库添加总计 [英] Add total from Access Database

问题描述

我正在制造一个计算器，该计算器将从列表框中获取一本书的书名，在链接的数据库中查找该书，然后计算该书的价格.然后，价格将计算为列表框中所有书籍的小计，然后加上税款和最终价格 全部显示在标签中.只需按一下按钮即可开始.我被困住了，这是我开始的地方，但是没有用.

I am making a calculator that will take a title of a book from a list box, find the book in a linked database and take the price of that book. The price would then be calculated as a subtotal of all the books in the list box and then add tax and a final total show in labels. It would all be started with the press of a button. I am stuck, this was where I started but it is not working.

 私有子Calc_Btn_Click(作为对象发送，作为EventArgs发送)处理Calc_Btn.Click
      点心作为Double
       For x As Integer = 0到Cart_List.Items.Count-1
           sum + = Val(Cart_List.Items.Item(x).ToString)
       Next

  Private Sub Calc_Btn_Click(sender As Object, e As EventArgs) Handles Calc_Btn.Click
        Dim sum As Double
        For x As Integer = 0 To Cart_List.Items.Count - 1
            sum += Val(Cart_List.Items.Item(x).ToString)
        Next

推荐答案

这是一个非常简单的问题，因此我认为这是家庭作业.

It is a very simple question therefore I think it is homework. 

您要做的是使用TableAdapter创建数据表

What you have to do is create a datatable with a TableAdapter

然后您得到一张桌子.您将表"设置为列表框的数据源

Then you get with that a table. That you set to the Table as datasource of the listbox

LB.DataSource =数据表

LB.DataSource = theDataTable

您设置为Displaymember的名称
LB.DisplayMember =名称"

The Name you set to the Displaymember
LB.DisplayMember = "Name"

，并以相同的方式向价值成员收取价格.

and in the same way the price to the valuemember.

处理索引更改事件的方法中现在唯一需要的代码是

The only code you need now in the method which handles the index changed event is

Sum += Cdec(LB.Value)

然后将sum设置为标签

and then set sum to the label

SubTot_lbl = Sum.ToString("9,99")(英语9.99)

SubTot_lbl = Sum.ToString("9,99") (in English 9.99) 

 

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