如何遍历 uwp 页面中的每个元素？

Question

I want to validate if any of the comboBoxes on the page have not been selected.

I have tried:

foreach (ComboBox combo in PageName)
{
    if (combo.SelectedIndex == -1)
    {
        // Activate Teaching Tip assosiated with this error to tell the user what needs changing
        NotSelected.IsOpen = true;
        return;
    }
}

However it says 'PageName' is a type which isn't valid in the given context.

Is there a way to achieve this?

Answer 1

You need to reference a panel which contains ComboBoxes:

foreach (UIElement item in grid.Children)
{
    // ...
}

Inside foreach loop check if an item is ComboBox then cast it to a ComboBox to perform some operation on it:

if (item is ComboBox)
{
    ComboBox comboBox = item as ComboBox;
    if (comboBox.SelectedIndex == -1)
    {
        // ...
    }
}

Place that teaching tip somewhere on the UI and hide it. Make it visible when item is not selected in a ComboBox:

foreach (UIElement item in grid.Children)
{
    if (item is ComboBox)
    {
        ComboBox comboBox = item as ComboBox;
        if (comboBox.SelectedIndex == -1)
            teachingTip.Visibility = Visibility.Visible;
    }
}