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How do I check whether my Generic List IsNullOrEmpty?

In my previous interview I have got one bumbarded question.
 
Q. Can I implement IsNullOrEmpty for my Generic collections/lists ?
Ans. Its out of C#. Unfortunately there is only one method which is of a String method String.IsNullOrEmpty() available, framework does not provide us such things. 
 
What is the solution for this.
A solution is only Extension Method, we just need to create an Extension Method which will provide the same facility: Here is the extension method:
  1. public static class CollectioncExtensionMethods  
  2.     {  
  3.         public static bool IsNullOrEmpty<T>(this IEnumerable<T> genericEnumerable)  
  4.         {  
  5.             return ((genericEnumerable == null) || (!genericEnumerable.Any()));  
  6.         }  
  7.   
  8.         public static bool IsNullOrEmpty<T>(this ICollection<T> genericCollection)  
  9.         {  
  10.             if (genericCollection == null)  
  11.             {  
  12.                 return true;  
  13.             }  
  14.             return genericCollection.Count < 1;  
  15.         }  
  16.     }  
Enjoy the benefit of these extension methods :) 
 
  1. var serverDataList = new List<ServerData>();  
  2.   
  3. var result = serverDataList.IsNullOrEmpty();//It will use IsNullOrEmpty<T>(this ICollection<T> gnericCollection)  
 
  1. var serverData = new ServerDataRepository().GetAll();  
  2.               
  3. // It will use IsNullOrEmpty<T>(this IEnumerable<T> genericEnumerable)  
  4. var result = serverData.IsNullOrEmpty();   
 
 Can you think what it will give when I call serverDataList.Count and when I call serverData.Count ?
 
Hint: One will give me O(n) while other O(1), enjoy :)