How do I do operations on an inherited base constructor in C#?
<p>Example</p>

<pre><code>public class ClassA
{
    public ClassA(string someString){}
}

public class ClassB : ClassA
{
    public ClassB(string someString):base(someString.ToLower()){}
}
</code></pre>

<p>I call the inherited ClassB constructor.  I pass in a null.  ToLower() throws an exception on a null.  I want to check for a null before that happens.  How can I do this?</p>
