VirtualCallInConstructorOrDestructor.qhelp

<!DOCTYPE qhelp PUBLIC
  "-//Semmle//qhelp//EN"
  "qhelp.dtd">
<qhelp>
<overview>
<p>Virtual calls or accesses in a constructor or destructor might not behave as expected. The 
constructor for the base class is always executed first, but in the context of the runtime type of 
the object. If a method is overridden in a sub type then that overridden method can be called from 
the constructor of the base type. This can lead to the methods of a class being called before the 
constructor of the class, which can have unexpected consequences.</p>

</overview>
<recommendation>
<p>Carefully check the virtual calls or accesses to make sure they will behave as expected. If 
possible, eliminate the virtual calls.</p>

</recommendation>
<example>
<p>In this example <code>DClass.Method()</code> is called before the <code>DClass</code> constructor is called. 
This is a problem because <code>DClass</code>'s version of <code>Method()</code> is not expecting to be 
called before the constructor.</p>
<sample src="VirtualCallInConstructorOrDestructor.cs" />

<p>This example outputs the following:</p>
<pre>Base constructor called.
D method called. Ready for method to be called? No
D constructor called.</pre>
</example>
</qhelp>