如何從visual basic中的列表框中獲取用戶輸入？

Question

我需要幫助從 ListBox（標記為 lstAge）獲取輸入。 我需要知道所以我可以將它轉換為 double 因為我想為正在使用的值做一個 If 語句。 我會附上我所擁有的以防萬一。

'''
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
     For count As Double = 16 To 100
     count = lstAge.Items.Add(count.ToString())
Next
    lstAge.SelectedIndex = 0
End Sub

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles btnSubmit.Click
        Dim age As Double

    If txtTicket.Text = "N" Or txtTicket.Text = "n" Then
        If age < 30 Then
            lblResult.Text = txtName.Text & ", your insurance cost will be $45. Keep Up the good driving!"
        Else
            lblResult.Text = txtName.Text & ", your insurance cost will be $30."
        End If
    Else
        lblResult.Text = txtName.Text & ", your insurance cost will be $85."
    End If
End Sub

'''

Answer 1

像這樣嘗試：

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
     For count As Double = 16 To 100
     count = lstAge.Items.Add(count.ToString())
Next
    lstAge.SelectedIndex = 0
End Sub

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles btnSubmit.Click
    Dim age As Double

    age = CDbl(lstAge.SelectedItem.ToString())

    If txtTicket.Text = "N" Or txtTicket.Text = "n" Then
        If age < 30 Then
            lblResult.Text = txtName.Text & ", your insurance cost will be $45. Keep Up the good driving!"
        Else
            lblResult.Text = txtName.Text & ", your insurance cost will be $30."
        End If
    Else
        lblResult.Text = txtName.Text & ", your insurance cost will be $85."
    End If
End Sub

在Button1_Click函數中，通過使用ListBox.SelectedItem獲取列表框中所選項目的值，將其轉換為字符串，然后使用CDbl將其轉換為雙精度值來設置age 。

這假設您的列表框沒有多列並且您一次選擇一項。

Answer 2

如果我理解你，你不知道如何從 ListBox 所選項目中獲取價值...

要從列表框中獲取值，您可以使用ListBox.SelectedItem 屬性：

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles btnSubmit.Click
    Dim currentage As Integer = DirectCast(lst.SelectedItem, Integer)
    Dim message As String = txtName.Text

    If txtTicket.Text.ToLower() = "n" Then
        Select Case currentage
            Case  16 to 30
                message &= ", your insurance cost will be $45. Keep Up the good driving!"
            Case else
                message &= ", your insurance cost will be $30."
        End Select
    Else
        message = &= ", your insurance cost will be $85."
    End If

    lblResult.Text =  message
End Sub