Is it impossible to verify whether an item in the listbox was selected?

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No, it is not impossible to verify whether an item in the listbox was selected. In fact, it is very common to do this in programming. You can use some event handlers or methods to verify if the user has selected an item from the list.

Here are some ways to do this in different programming languages:

C#:

You can use the SelectedIndexChanged event of the ListBox control to determine if an item was selected. Here's an example:

private void listBox1_SelectedIndexChanged(object sender, EventArgs e)
{
    if (listBox1.SelectedIndex != -1)
    {
        // An item was selected
    }
}

Java:

You can use the getSelectedIndex() method of the JList class to determine if an item was selected. Here's an example:

private void listValueChanged(ListSelectionEvent e) {
    if (!e.getValueIsAdjusting() && list.getSelectedIndex() != -1) {
        // An item was selected
    }
}

Python:

You can use the get() method of the Tkinter Listbox widget to determine if an item was selected. Here's an example:

def callback(event):
    if listbox.curselection():
        # An item was selected

listbox.bind("<<ListboxSelect>>", callback)

Overall, verifying whether an item in the listbox was selected is possible and can be done using different methods in different programming languages.