C# set inherited class equal to base class
<p>if I have a parent class:</p>

<pre><code>public class ParentClass
{
  public string ParentStr = string.empty;
}
</code></pre>

<p>and a child class:</p>

<pre><code>public class ChildClass : ParentClass
{
  public string ChildStr = string.empty;
}
</code></pre>

<p>Say later in my code I have an instance of ParentClass</p>

<pre><code>ParentClass parentClass = New ParentClass() { ParentStr = "something" } 
</code></pre>

<p>Is it possible to create an instance of the ChildClass from the ParentClass? Something to the effect of:</p>

<pre><code>ChildClass childClass = (ChildClass)parentClass
</code></pre>
