Passing in null values to a recursive method
<p>I have a method which I want to call itself if a certain condition is true. Initially the method accepts one parameter whose value changes before said condition is reached.</p>

<pre><code>public static void Build(string str)
{
    var tree = XmlBuilder.Load();
    foreach (var section tree.Sections)
    {
        str += section.Name;
        foreach (var variable in tree.Sections[section].Variables)
        {
            //
        }
    }
    if (tree.Sections[section].Sections.Count &gt; 0)
    {
        // here I want to call Build(null)
    }
}
</code></pre>

<p>I'm not checking for a null value yet - just wanna know if this is possible first? If I say <code>if (str==null) { }</code> that wouldn't work because str has a value, correct? Is there any way of checking what value was PASSED IN to the method rather?</p>
