Question

用户选择比萨饼，大小等，并将比萨饼添加到篮子中（列表视图）。表单清除但用户可以再次单击添加按钮，这会将不需要的行添加到列表视图中。我已经尝试实现一个for循环来检查是否在添加新记录之前选中了复选框。结果，想要的记录添加到列表视图，但消息弹出x次。单击按钮时没有选中复选框也会出现此重复消息框。请帮忙吗？

'Add Pizza to Listview
Private Sub btnAddPizza_Click(sender As Object, e As EventArgs) Handles btnAddPizza.Click
    Dim itemname As String
    Dim price As Decimal
    Dim qty As Integer
    grandtotal = 0
    'Add to list view
    For Each rb1 In {rb01, rb02, rb03, rb04, rb05, rb06, rb07, rb08, rb09, rb10, rb11, rb12, rb13, rb14, rb15}
        If rb1.Checked = True Then
            itemname = GetCheckedItem()
            price = CDec(pizzacost)
            qty = 1
            ListView1.Items.Add(New ListViewItem({itemname, qty, price}))
        ElseIf rb1.Checked = False Then
            MsgBox("No pizza is selected", MsgBoxStyle.Information)
        End If
    Next
    'recalculate grandtotal (bottom of listview)
    For Each x As ListViewItem In ListView1.Items
        grandtotal += CDec(x.SubItems(2).Text)
    Next
    lblGrandTotal.Text = "£ " & grandtotal
    'Discard Pizza selection
    For Each rb In {rb01, rb02, rb03, rb04, rb05, rb06, rb07, rb08, rb09, rb10, rb11, rb12, rb13, rb14, rb15}
        rb.Checked = False
    Next
    For Each rb In {rbSmall, rbMedium, rbLarge, rbSuper}
        rb.Checked = False
    Next
    For Each rb In {rbDeep, rbThin, rbStuffed}
        rb.Checked = False
    Next
    lblTotalPizza.Text = ""
    itemname = ""
    price = 0
End Sub

Answer 1

目前还不清楚你要做的是什么，但我认为你的问题在于你只想让你的for循环中的代码执行一次。换句话说，而不是：

For Each rb In radioButtons
    If rb.Checked Then    ' This happens once per radio button
        ' Add item
    Else
        ' Show Error
    End If
Next

你想做这样的事情：

Dim found As Boolean
For Each rb In radioButtons
    If rb.Checked Then    ' This happens once per radio button
        found = True
    End If
Next
If found Then    ' This happens once after the loop is done 
    ' Add item
Else
    ' Show Error
End If

然而，LINQ通过它的Any扩展方法使这样的事情更容易：

If radioButtons.Any(Function(rb) rb.Checked) Then
    ' Add item
Else
    ' Show Error
End If

防止对listview进行多次添加

1 个答案: