取消选中一个项目，然后选择全部＆＃34; Windows窗体上CheckedListBox的选项

Question

我添加了一个包含一些名称和全选选项的复选框列表。当我选择（全选）选项时，我可以选中复选框列表中的所有复选框。

问题在于，每当我取消选中复选框列表中的任何选项时，我都无法取消选中（全选）选项。

以下是为（全选）功能附加的vb.net代码。

Private Sub ChkLB_dl_name_cb_ItemCheck(sender As Object, e As ItemCheckEventArgs) Handles ChkLB_dl_name_cb.ItemCheck        
    If e.Index = 0 Then
        Dim newCheckedState As Integer = e.NewValue
        For i As Integer = 1 to ChkLB_dl_name_cb.Items.Count - 1
            Me.ChkLB_dl_name_cb.SetItemCheckState(i, newCheckedState)
        Next
    End If 
End Sub

以下是Windows表单上复选框列表的图片，供您参考。

Answer 1

一般情况下，我会使用Boolean变量来避免为您以编程方式更改的每个项调用此处理程序。这也将解决您无法取消选中第一项的问题：

Private updatingListProgramatically As Boolean = False

Private Sub ChkLB_dl_name_cb_ItemCheck(sender As Object, e As ItemCheckEventArgs) Handles ChkLB_dl_name_cb.ItemCheck
    If updatingListProgramatically Then Return

    If e.Index = 0 Then
        updatingListProgramatically = True
        For i As Integer = 1 To ChkLB_dl_name_cb.Items.Count - 1
            Me.ChkLB_dl_name_cb.SetItemCheckState(i, e.NewValue)
        Next
    Else
        Dim checked As Boolean = e.NewValue = CheckState.Checked
        If Not checked Then
            updatingListProgramatically = True
            Me.ChkLB_dl_name_cb.SetItemCheckState(0, CheckState.Unchecked)
        End If
    End If

    updatingListProgramatically = False
End Sub

Else块似乎就是你所要求的。

Answer 2

尝试为第一个添加Else＆＃39; If＆＃39;条件并添加第二个＆＃39;如果＆＃39;声明是否＆＃34;全选＆＃34;复选框是否未选中。

cd /path/to/folder && ls -1t | tail -n +6 | sudo xargs rm -rf

Answer 3

如下所示，您应该获得所需的功能：

Private Sub ChkLB_dl_name_cb_ItemCheck(sender As Object, e As ItemCheckEventArgs) Handles ChkLB_dl_name_cb.ItemCheck
    If e.Index = 0 Then
        Dim newCheckedState As Integer = e.NewValue
        For i As Integer = 1 To ChkLB_dl_name_cb.Items.Count - 1
            Me.ChkLB_dl_name_cb.SetItemCheckState(i, newCheckedState)
        Next
    Else
        'Remove the event-handler to prevent the ItemCheck-method from being called again
        RemoveHandler ChkLB_dl_name_cb.ItemCheck, AddressOf ChkLB_dl_name_cb_ItemCheck

        'If the item is being checked and all items are checked
        '(except "Select All"), then check "Select All"
        If e.NewValue = CheckState.Checked AndAlso
           ChkLB_dl_name_cb.CheckedItems.Count + 1 = ChkLB_dl_name_cb.Items.Count - 1 Then
            'Check "Select All"
            ChkLB_dl_name_cb.SetItemCheckState(0, CheckState.Checked)
        Else
            'Uncheck "Select All"
            ChkLB_dl_name_cb.SetItemCheckState(0, CheckState.Unchecked)
        End If

        'Re-Add the handler
        AddHandler ChkLB_dl_name_cb.ItemCheck, AddressOf ChkLB_dl_name_cb_ItemCheck
    End If
End Sub