Working with Collections - 21 | C# Fundamentals: Development for Absolute Beginners

Collections are a more powerful form of arrays. In this lesson we demonstrate an "old style" collection (pointing out its limitations) as well as several of the newer, strongly typed generic collections (List<T> and Dictionary<T1, T2>) utilizing the generics syntax.

Download the source code for Working with Collections

Follow the Discussion

Follow
Oops, something didn't work.

Try again?

Sign In to be begin to follow these comments

What does this mean?
Following an item on Channel 9 allows you to watch for new content and comments that you are interested in. You need to be signed in to Channel 9 to use this feature.

Getting "follow" information

Stop following these comments

Start following these comments

What does this mean?
Following an item on Channel 9 allows you to watch for new content and comments that you are interested in and view them all on your notifications page.

Removing your "follow"

Setting up your "follow"

Did you know you can
sign up for email notifications?
- Subscribe to this comments

DeveloperDZ MSP

Dec 05, 2011 at 12:03 PM

nice job, thank you
MihaiMorariu
Jan 05, 2012 at 2:30 PM
Hello Mr. Tabor,

First of all, thank you for the series. It's awesome and has helped me a lot.
There is one thing, though, that I don't understand in this video. Why is it that when you are creating a Car object you are using the sytnax
- Car car1 = new Car() (with parantheses)
but when you are initializing the collection you are using
- new Car { Make = "Oldsmobile", Model = "Cutlas Supreme" } (without parantheses)
I hope my question does not sound stupid, but why exactly do we use parantheses in one case but do not in the other?

Thank you,

Mihai Morariu
fred

Jan 05, 2012 at 11:01 PM

Hi Mihai,

I'll give it a go & try to explain, as I just watched the tutorial.

First they are 2 different processes, so therefore using different syntax... as defined by the C# designers.

The brackets are for declaring which "Constructor", to use when creating an instance. A constructor with () and no parameters usually means the default 'internal' constructor will be evoked. Go back to the first lesson on classes for more info.

The curly brackets are used to assigned data to the named fields, just an alternate way instead of in a constructor.

So

List<Car> myList = new List<Car>()

Will create a List of Cars called myList, again invoking the default 'internal' constructor. So there is no need for a constructor to be explicitly called for each Car element.

But the each car element in the list is assigned it's initial data values, instead of through a constructor.

I hope that helps till you get a reply from Bob.

And thanks Bob for sharing your knowledge, as I'm self taught through reading books, having some things explained has helped & the various tips & tricks.
fred

Jan 05, 2012 at 11:22 PM

I think I spoke too soon, in the next video the following is used!

List<Car> myCars = new List<Car>() {
new Car() { Make="BMW", Model="550i", Color=CarColor.Blue, StickerPrice=55000, Year=2009 },
....
};

So I'll leave it to Bob!
MihaiMorariu
Jan 06, 2012 at 2:10 AM
Hello Fred,

Thank you for your reply.
I was not referring to the curly braces, but the parantheses. What I'm saying is that in the beginning of the video the "car1" object is initialized with the following line:
- Car car1 = new Car();
As you said, we are using the paranthesis here since we are calling the default constructor. However, later in the video (21:00), when initializing the collection, Mr. Tabor is using the following line:
- List<Car> myList = new List<Car> {
new Car { Make = "Oldsmobile", Model = "Cutlas Supreme" } ...
See the difference? There is no () here when creating the Car object. This is what I was talking about.

Regards,
Mihai
Duncanma "yeah that's awful close, but that's not why I'm so hard done by"
Jan 06, 2012 at 10:02 AM
@MihaiMorariu: Mihai, this is just a syntax difference and is really personal preference. When you create an object and pass in a list of initial values, the parantheses can be skipped and they are assumed. So
```
            Car car = new Car() {color = "red"};
```
and
```
            Car car = new Car {color = "red"};
```
are functionally equivalent. Personally I use the first, because the second looks odd to me (and apparently to you as well ), but either will work. You can see this on MSDN at http://msdn.microsoft.com/en-us/library/bb384062.aspx and if you look at the various code samples you will see that they use both forms.

Duncanma "yeah that's awful close, but that's not why I'm so hard done by"

Jan 06, 2012 at 10:09 AM

for those that are interested, the two lines produce the same IL (intermediate language, the code that C# is compiled into so that the .NET runtime can execute it)

  IL_0001:  newobj     instance void ConsoleApplication1.Car::.ctor()
  IL_0006:  stloc.2
  IL_0007:  ldloc.2
  IL_0008:  ldstr      "red"
  IL_000d:  stfld      string ConsoleApplication1.Car::color
  IL_0012:  ldloc.2
  IL_0013:  stloc.0


  IL_0014:  newobj     instance void ConsoleApplication1.Car::.ctor()
  IL_0019:  stloc.3
  IL_001a:  ldloc.3
  IL_001b:  ldstr      "red"
  IL_0020:  stfld      string ConsoleApplication1.Car::color
  IL_0025:  ldloc.3
  IL_0026:  stloc.1

MihaiMorariu

Jan 06, 2012 at 10:57 AM

Thank you for your help, Duncan ! It makes sense now.

Regards,
Mihai
BobTabor

Jan 12, 2012 at 11:06 AM

@Duncanma:Wow, nice work there. Thanks for helping out. For the record, I may have temporarily lost my mind because I would prefer to use the (), too! Sorry for the confusion, but sometimes it's those mistakes that help you learn something (like I learned with your IL example!)
golnazal HEY HEY HEY

May 02, 2013 at 8:08 AM

opening thread.
Varun

May 03, 2013 at 6:01 AM

Hi Bob,

Thank you for this amazing lesson, it is of great help to me.Although i have a query

in line 73 of your code
Console.WriteLine(myDictionary["Geo"].Model);

i accidentally wrote the following

Console.WriteLine(myDictionary["Geo"]);

and got the following display on the console

"Collections.Car"

are we not supposed to get some kind of error. I did not understand how that output came to be. I understand that myDictionary["Geo"] points to a particular car type object in the dictionary.