title: SerializationInfo Instance Is Never Null?
body: <p>I'm messing around with writing custom exceptions and implementing serialization for them.  I've noticed that if I null check the instance of SerializationInfo before accessing one of its members, ReSharper tells me the check is redundant and that the instance is known to be not null.  It's not a value type, but poking around on the <a href="http://referencesource.microsoft.com/#mscorlib/system/runtime/serialization/serializationinfo.cs" rel="nofollow">Reference Source</a> showed me there is no default constructor.  Is this how ReSharper can tell it won't be null?  Is there some other reason?  Is this possibly a bug?</p>