C# Puzzle No.12 (intermediate)

Consider following class which stores the information about external urls.

   1: class LinkInfo

   2: {

   3:      public int    Ord { get; set; }

   4:      public string Url { get; set; }

   5: }

In your application you somehow retrieve the list of such items:

   1: List<LinkInfo> l = new List<LinkInfo>()

   2:      { 

   3:        new LinkInfo() { Ord = 1, Url = "" },

   4:        new LinkInfo() { Ord = 2, Url = "test1" },

   5:        new LinkInfo() { Ord = 3, Url = "test1" },

   6:        new LinkInfo() { Ord = 4, Url = "test2" },

   7:        new LinkInfo() { Ord = 5, Url = "" }

   8:      };

Your goal is to use Linq to filter this list in a special way:

• if the Url is empty - the item is always returned


• if the Url is nonempty - only one item with such Url is returned

In the above case the Linq expression should return:

   1: { 

   2:   new LinkInfo() { Ord = 1, Url = "" },

   3:   new LinkInfo() { Ord = 2, Url = "test1" },

   4:   new LinkInfo() { Ord = 4, Url = "test2" },

   5:   new LinkInfo() { Ord = 5, Url = "" }

   6: };

or

   1: { 

   2:   new LinkInfo() { Ord = 1, Url = "" },

   3:   new LinkInfo() { Ord = 3, Url = "test1" },

   4:   new LinkInfo() { Ord = 4, Url = "test2" },

   5:   new LinkInfo() { Ord = 5, Url = "" }

   6: }

 

How effective is your solution? Can you not only think of just a solution but of an effective one?