UselessNullCoalescingExpression.qhelp

<!DOCTYPE qhelp PUBLIC
  "-//Semmle//qhelp//EN"
  "qhelp.dtd">
<qhelp>
<overview>
<p>It is rare, but not impossible, to write a null-coalescing expression whose left and right operands 
both do the same thing. The consequences are typically unfortunate - since a null-coalescing 
expression is generally used to do something special when a variable is null, failing to handle that 
(evidently expected) case often leads to a <code>NullReferenceException </code>, either immediately or 
later in the program's execution.</p>

</overview>
<recommendation>
<p>Rewrite the <code>else</code> part of the null-coalescing expression to provide a suitable 
substitute if the variable is null.</p>

</recommendation>
<example>
<p>This example demonstrates a simple class designed to generate random numbers. At its core is an 
instance of <code>Random</code> called <code>generator</code>. In order to be more efficient, the 
programmer has chosen not to initialize the generator until it is first needed. Due to both sides of 
the null-coalescing expression being the same, <code>generator</code> is never initialized and a <code>
NullReferenceException</code> occurs when attempting to call <code>Next</code>.</p>
<sample src="UselessNullCoalescingExpression.cs" />
</example>
</qhelp>