Does C# have IsNullOrEmpty for List/IEnumerable?

Question

I know generally empty List is more prefer than NULL. But I am going to return NULL, for mainly two reasons

1. I have to check and handle null values explicitly,

Answer 1

Late update: since C# 6.0, the null-propagation operator may be used to express concise like this:

if (  list?.Count  > 0 ) // For List
if ( array?.Length > 0 ) // For Array

or, as a cleaner and more generic alternative for IEnumerable:

if ( enumerable?.Any() ?? false )

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Note 1: all upper variants reflect actually IsNotNullOrEmpty, in contrast to OP question (quote):

Because of operator precedence IsNullOrEmpty equivalents look less appealing:
if (!(list?.Count > 0))

Note 2: ?? false is necessary, because of the following reason (summary/quote from this post):

?. operator will return null if a child member is null. But [...] if we try to get a non-Nullable member, like the Any() method, that returns bool [...] the compiler will "wrap" a return value in Nullable<>. For example, Object?.Any() will give us bool? (which is Nullable), not bool. [...] Since it can't be implicitly casted to bool this expression cannot be used in the if

Note 3: as a bonus, the statement is also "thread-safe" (quote from answer of this question):

In a multithreaded context, if [enumerable] is accessible from another thread (either because it's a field that's accessible or because it's closed over in a lambda that is exposed to another thread) then the value could be different each time it's computed [i.e.prior null-check]