为多个组合框设置相同的SelectedIndex值 [英] Setting same SelectedIndex value for multiple combobox

问题描述

我有一个表格，其中有23个组合框。为每个组合框编写 SelectedIndex = -1 肯定可以，但是我想知道是否还有其他方法可以按照下面的示例进行操作。 ？

I have a form where i have 23 Comboboxes. Writing SelectedIndex=-1 for every combobox will definitely work but i want to know whether there's any other way of doing it as done in below given example. ?

  For Each ctl As Control In (GroupBox1.Controls)
            If TypeOf ctl Is TextBox Then
                ctl.Text = ""
            End If            
 Next

我尝试了此操作，


如果TypeOf ctl是ComboBox则
ctl.selectedIndex = -1
结束

但是它不起作用。

i tried this,

If TypeOf ctl Is ComboBox Then ctl.selectedIndex=-1 End If

but it doesn't works. Please help me out.

推荐答案

在您的示例中，您的 ctl 变量为 Control 而不是 Combobox ，因此它没有 SelectIndex 属性-尽管您可以使用 DirectCast（ctl，Combobox）抛弃它。

In your example your ctl variable is a Control and not a Combobox so it does not have the SelectIndex property - though you could have casted it back with DirectCast(ctl, Combobox).

For Each ctl As Control In (GroupBox1.Controls)
  If TypeOf ctl Is Combobox Then
    DirectCast(ctl, Combobox).SelectedIndex = -1
  End If            
Next

或者为您的循环创建一个特定于类型的控制循环。

Or create a loop of type specific control for your loop. No need to check type here.

Dim cbs = GroupBox1.Controls.OfType(Of Combobox)()
For Each cb In cbs
 cb.SelectedIndex = -1
Next

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