Introduction
When Generics came out in Visual Studio 2005, the
new List object was introduced. This feature was a new collection object that also gave you
the ability to sort records based on whatever criteria you wanted. There was also a new coding feature that came
out called “anonymous functions” which basically allowed you to plop a blob of
code in a parameter of another function. The Sort function was a big step in sorting
collections, much simpler than in Visual Studio 2003 but it still a bit jankie.
Sorting in Visual Studio 2005
So let's take a look at how to do this old way and then look at some new ways we can do the same thing in Visual Studio 2008.
30 public enum SortDirection
31 {
32 Ascending = 1,
33 Descending = -1
34 }
35
36
37 public List<GuestDto> SortLastNameUsingAnonymousFunction()
38 {
39 if (guests == null)
40 return null;
41
42 guests.Sort(new Comparison<GuestDto>(delegate(GuestDto guest1, GuestDto guest2)
43 {
44 return Convert.ToInt32(SortDirection.Ascending) * guest1.LastName.CompareTo(guest2.LastName);
45 }));
46
47 return guests;
48 }
Even after having done this many times, I still need to refer
to an example before doing it because it is just not that intuitive.
Using Lambda Expressions in the Same Example
Now let's look at a cleaner way to do this that even I can remember.
50 public List<GuestDto> SortLastNameUsingLambdaExpressions()
51 {
52 if (guests == null)
53 return null;
54
55 guests.Sort((guest1, guest2) =>
56 Convert.ToInt32(SortDirection.Ascending) * guest1.LastName.CompareTo(guest2.LastName));
57
58 return guests;
59 }
Essentially the way it works is the parameters are
placed on the left side of the => statement and the body of the code you
want to execute is on the right. All
the types (including guest1, guest2, the new Comparison object , and the
delegate and return statements) are automatically determined by the compiler so
you do not need to specify it. So the
Lambda Expression is a nice way to abbreviate anonymous methods and make the
code more readable.
Adding Linq to the Equasion
When
I mentioned to my team the neat way sorting which is easier to code, a co-worker
and friend Mike Bosch (great blog here) showed me an even better
approach by just referencing the Linq namespace.
62 public List<GuestDto> SortLastNameUsingLinqLambdaExpressions()
63 {
64 if (guests == null)
65 return null;
66
67 List<GuestDto> sortedGuests = guests.OrderBy(g => g.LastName).ToList();
68
69 return sortedGuests;
70
71 }
To which in the
immortal words of Bill and Ted's Excellent Adventure, I say "PARTY ON DUDES!"
