Getting the text value selected in at ListBox in C#

Question

I have a list box

  <Label Content="Report" HorizontalAlignment="Left" Height="47" Margin="36,75,0,0" VerticalAlignment="Top" Width="63"/>
    <ListBox x:Name="ListBox1" HorizontalAlignment="Left" Height="121" Margin="84,75,0,0" VerticalAlignment="Top" Width="102" SelectionChanged="ListBox_SelectionChanged" SelectedIndex="-1">
        <ListBox Height="100" Width="100" SelectionChanged="ListBox_SelectionChanged_1">
            <ListBoxItem x:Name="ListBoxFAT" Content="FAT"/>
            <ListBoxItem x:Name="ListBoxNUMI" Content="NUMI"/>
            <ListBoxItem x:Name="ListBoxSSID" Content="SSID"/>
            <ListBoxItem x:Name="ListBoxFact" Content="FACT"/>
        </ListBox>
    </ListBox>

This was created by dragging the listbox icon from the tool bar. I added items and their values.
Now I am trying to just get the text value of the selected item.

 private void ListBox_SelectionChanged_1(object sender, SelectionChangedEventArgs e)
    {
        string text = (string)ListBox1.SelectedValue;
        MessageBox.Show(text);

I have also tried SelectedItem

string text = (string)ListBox1.SelectedItem;

But the message box is always blank.
This should be simple, but I have been working on it for hours, and trying every suggestion or answer on stackoverflow. Most suggestions do not even compile. For example:

  string selected = listBox1.GetItemText(listBox1.SelectedValue);

Will not compile. GetItemText is not found. I am using Visual Studio 17. "'ListBox does not contain a definition for 'GetItemText'..."

Any thoughts? Please advise. Thanks.

Thanks for the comment, Charles. I did that. Playing further, now I get

 System.InvalidCastException: 'Unable to cast object of type 'System.Windows.Controls.ListBoxItem' to type 'System.String'.' string text = (string)ListBox1.SelectedItem; 

Answer 1

In the markup, SelectedIndex is set to -1 which means there is no selection. In this case, SelectedValue and SelectedItem both return null. You can solve this either by setting SelectedIndex to a value between 0 and 3 or by preparing your code to cope with a null value in SelectedValue and SelectedItem , eg

string text = (ListBox1.SelectedItem as ListBoxItem)?.Content?.ToString();

This won't raise an error so that the user can select an item afterwards. With a selection, the text should be displayed as expected.

Answer 2

As indicated by Charles May, your XAML shows that your ListBox is within another ListBox, which is why you're getting errors being raised..

The event being called "ListBox_SelectionChanged_1" is bound to the ListBox object inside ListBox1, which is unnamed.

I believe that the behaviour you are looking for would be fixed like this:

XAML:

<Label Content="Report" HorizontalAlignment="Left" Height="47" Margin="36,75,0,0" VerticalAlignment="Top" Width="63"/>
    <ListBox x:Name="ListBox1" HorizontalAlignment="Left" Height="121" Margin="84,75,0,0" VerticalAlignment="Top" Width="102" SelectionChanged="ListBox_SelectionChanged" SelectedIndex="-1">            
        <ListBoxItem x:Name="ListBoxFAT" Content="FAT"/>
        <ListBoxItem x:Name="ListBoxNUMI" Content="NUMI"/>
        <ListBoxItem x:Name="ListBoxSSID" Content="SSID"/>
        <ListBoxItem x:Name="ListBoxFact" Content="FACT"/>            
    </ListBox>

Code Behind:

private void ListBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
   string text = ((sender as ListBox)?.SelectedItem as ListBoxItem)?.Content.ToString();
   MessageBox.Show(text);
}

Or at least something close to this solution.