订购食物清单 [英] Order food list

问题描述

我如何计算列表框中的所有项目

how do i compute all of item in listbox

如果单选按钮1被选中，则将总计增加10 $
如果列表框，组合框和乘员组名称为空白，则会弹出错误，

if radiobutton1 is check add 10$ to total
if listbox, combobox, and crewname is blank pop up error,

我已经做了什么

what i already done

Public Class Form1



    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        ComboBox1.Items.Add("water")
        ComboBox1.Items.Add("ice")
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim i As Integer


        MsgBox("Crew Name: " & i, 64)

    End Sub


    Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
        If ComboBox1.SelectedItem = ("water") Then
            ListBox1.Items.Add("water $1")
        ElseIf ComboBox1.SelectedItem = ("ice") Then
            ListBox1.Items.Add("ice $2")
        End If


    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        ListBox1.Items.Clear()

    End Sub

    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        Me.Close()
    End Sub
End class

请帮助

推荐答案

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http://i.imgur.com/gH8aBAq.png

像这样

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