C# Method signature object reference
<p>Lets say I have a base class and child like this:</p>

<pre><code>class BaseType
{
   string Name{get;set;}
   string AddressLine1 {get;set;}
   string PostalCode {get;set;}
}


class ChildType : BaseType
{
    string extrafield {get;set;}
}
</code></pre>

<p><strong>Edit:</strong></p>

<p>My custom Update method is the same for both objects for all but the one extra field. These objects are used in WCF services, so reusing a custom SET WCF Service is what I'm trying to do.</p>

<p>So I would pass in either a <code>BaseType</code> or a <code>ChildType</code>; be able to access the base properties for either object and do what ever logic.</p>

<p>I'm trying to reduce duplication of code. </p>
