I'm trying to figure out how to add an `if`/`else` statement so that when I press the button it doesn't add duplicates to my `listBox` 

There's already an if statement but it doesn't work.

Here is the code for the button.

```
private void btnSort_Click(object sender, RoutedEventArgs e)
{
    if (lstbxResults.Items.Contains(lstbxResults.Items))
    {
        foreach (var Sort in lstbxResults.Items)
            Sorting.Add(LSort);

        Sorting.Sort();
        lstbxResults.Items.Clear();

        foreach (var GSort in Sorting)
            lstbxResults.Items.Add(lSort);
    }
}

```