如何使用if语句与包含strName字符串的列表框进行比较 [英] How to compare with ListBoxes that contains string for strName using if statements

问题描述

我是编程的初学者，现在我在大学里正在讲视觉基础的编程课程，而且我正在写一个有关CD Collection的程序，该程序可以防止用户将CD名称复制到列表框中.三种类型是CD名称，艺术家和价格.

现在，我输入其中三个(使用输入框)​​以添加并存储到列表框(链接到"names.txt"文件).

现在，我想添加另外三个，当他们问我CD名称时，如果我键入与已经存储在列表框中的CD名称相同的CD名称，它应该显示我已经输入了CD名称.这是我遇到的困难.

如何使用if语句将strName设置为与列表框中的strName进行比较?

任何帮助表示赞赏.

Hi, I''m a beginner of programming and I''m talking visual basic programming course now at college, and I''m writing a program about the CD Collection that prevents user to duplicate CD name into the listbox. The three types are CD name, artists, and price.

Now I input three of those(using inputbox) to add and store into listbox(linked to "names.txt" file).

Now I want to add another three, and when they ask me for the cd name, and if I type the same cd name as the one that is already stored in the listbox, it should display that I already entered the CD name. This is the one I''m having difficult with.

How can I set the strName to compare with the strName''s in the listbox using the if statement?

Any help is appreciated.

Private Sub btnAdd_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnAdd.Click
    ' adds CD information to the list box

    ' declare variables
    Dim strName As String
    Dim strArtist As String
    Dim strPrice As String
    Dim strConcatenatedInfo As String
    Dim dblPrice As Double
    ' get the CD information
    strName = InputBox("CD name:", "CD Collection")


    If strName.Contains(strName.PadRight(40)) Then


        MessageBox.Show("Duplicate Name",
                        "CD Collection",
                        MessageBoxButtons.OK,
                        MessageBoxIcon.Information)

    Else
        strArtist = InputBox("Artist:", "CD Collection")
        strPrice = InputBox("Price:", "CD Collection")

        ' format the price, then concatenate the
        ' input items, using 40 spaces for the
        ' CD name, 25 spaces for the artist name,
        ' and 5 spaces for the price
        Double.TryParse(strPrice, dblPrice)
        strPrice = dblPrice.ToString("N2")
        strConcatenatedInfo = strName.PadRight(40) &
            strArtist.PadRight(25) & strPrice.PadLeft(5)
        ' add the information to the list box
        lstCds.Items.Add(strConcatenatedInfo)
    End If

End Sub

推荐答案

If strName.Contains(strName.PadRight(40)) Then

您正在尝试将strName与自身进行比较.您想将其与列表框中的现有项目进行比较.

顺便说一句:您在学习时应该指出，匈牙利符号(变量的三个字母前缀)已经过时了几年.

You are trying to compare strName against itself. You want to compare it against existing items in the listbox.

BTW: As you are just learning it should be pointed out that Hungarian notation, the three letter prefix to your variables, has been outdated for several years now.

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