what does value ?? 0 means in c# code
<pre><code>get { return _a.B; }

set
{
   if (( _a.B.Equals(value ?? 0) != true ))
   {
      _a.B= value ?? 0;
   }
}
</code></pre>

<p>I have coded the above code in c#. In the above code what does (value ?? 0) != true mean??</p>
