Definition

Action<int> example1 =
   (int x) => Console.WriteLine("Write {0}", x);
Action<int, int> example2 =
   (x, y) => Console.WriteLine("Write {0} and {1}", x, y);
Action example3 =  
   () => Console.WriteLine("Done");

• DotNetPerls: Action
• MSDN: Action of Delete
• StackOverflow: Use of Action Delete in C#
• WPF UI Update from Background Threads