This post originated from an RSS feed registered with .NET Buzz by Scott Hanselman. Original Post: Wesner's thoughts on Collection versus List Feed Title: Scott Hanselman's ComputerZen.com Feed URL: http://radio-weblogs.com/0106747/rss.xml Feed Description: Scott Hanselman's ComputerZen.com is a .NET/WebServices/XML Weblog. I offer details of obscurities (internals of ASP.NET, WebServices, XML, etc) and best practices from real world scenarios. Latest .NET Buzz Posts Latest .NET Buzz Posts by Scott Hanselman Latest Posts From Scott Hanselman's ComputerZen.com

Wesner offers his thoughts on my question, What's the difference between System.Collections.Generic.Collection and System.Collections.Generic.List?

I think there are two possible reasons.

• Collection<T> appears to be a replacement for CollectionBase, which provided virtual methods to detect insertions, deletions and changes.
• The new List class no longer provides any virtual methods as did the original ArrayList for performance reasons..
  [Wesner Moise]

He also educates us on some of the differences between List<T> and the 2.0 ArrayList.

• List<T> does not use any virtual methods. As a result, a number of methods such as the list indexer methods can now be inlined.
• With the default constructor, List<T> and Whidbey ArrayList do not allocate any memory for its items, so an empty list represents a very compact object--comparable in size to an empty array. (8 bytes for Array, 12 bytes for List, 16 bytes for Whidbey ArrayList) It uses the empty array trick that I wrote about in an earlier post. In contrast, earlier versions of ArrayList would allocate space for 16 items by default.
• The initial buffer size when an item is actually added is 4 items not 16 as before.
• List<T> returns an struct-based enumerator, so that iterating through foreach now involves no memory allocations at all.
  [Wesner Moise]