how to return false if string has null or white space in c#
<p>I cannot return null because my <code>Hlist</code> is a non nullable type. What else can I return in the place of null?</p>

<pre><code>HList findHListentry(string letter)
{
    if (string.IsNullOrWhiteSpace(letter))
    {
        HList result = listentry.Find(delegate(HList bk)
                       {
                           return bk.letter == letter;
                       });
        return result;
    }
    else
    {
        return ?;
    }
}
</code></pre>
