What is this syntax?

Question

0.00/5 (No votes)

See more:

C#

this.Add(new TabPage
{
    Text = text
});

I saw this after decompiling the source for TabControl. I can sort of infer what it's doing, but I've never seen an object being created like that before.

C#

new TabPage { Text = text };

Posted 30-Jan-12 10:48am

agent154

Add a Solution

Comments

Sergey Alexandrovich Kryukov 30-Jan-12 17:16pm

So what? What is your question? Any concerns about it? Why?
--SA

agent154 30-Jan-12 17:29pm

I never said there was a problem with it. I just haven't seen it before.

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Sergey Alexandrovich Kryukov · Accepted Answer · 2012-01-30T11:16:00

Solution 3

Well, now you see it. What's so special about it? :-)

Please see it in the specification of C# 3.0 (I believe this syntax was introduced in this version): http://msdn.microsoft.com/en-us/library/ms364047%28v=vs.80%29.aspx#cs3spec_topic5[^], locate the section "Object Initializers".

This is a pretty funny discussion related to coding styles using this feature: http://stackoverflow.com/questions/2574725/is-it-bad-to-use-initializer-block[^].

I personally think there is nothing wrong in it, even though I understand concerns of those warning against the practice of using those block object initializers. Many language features can be abused or, just the opposite, reasonably used, depending on the situation.

—SA

Posted 30-Jan-12 11:16am

Sergey Alexandrovich Kryukov

Comments

Espen Harlinn 30-Jan-12 17:25pm

Reasonable reply, absolutely deserving a 5 in this situation :)

Sergey Alexandrovich Kryukov 30-Jan-12 17:27pm

Thank you, Espen.
--SA

Sander Rossel 30-Jan-12 17:29pm

Nice discussion. The msdn article is a hard read due to the format. Good links though.
My 5!

Sergey Alexandrovich Kryukov 30-Jan-12 17:34pm

Thank you Naerling.
You know, getting precise information is always more difficult than something vague, but more valuable... :-)
Anyway, you added very adequate code samples explaining things.
Teamwork!
--SA

Sander Rossel 30-Jan-12 17:39pm

Nice working with you! :)

Sergey Alexandrovich Kryukov 30-Jan-12 18:29pm

Thank you. Likewise. :-)
--SA

BillWoodruff 30-Jan-12 22:20pm

Very reasonable answer, SAK, +5. I have made limited use of this new syntax, so far (old habits are resistant to change), but it does make code more readable: just looking at the parameter list alone of a method call, you know the names of the variables.

I'd highly recommend using this for beginners, or, if I were teaching, for students, as a useful self-discipline.

Sergey Alexandrovich Kryukov 30-Jan-12 23:06pm

Agree; thank you, Bill.
--SA

Sander Rossel · Accepted Answer · 2012-01-30T11:22:00

Solution 4

Actually, it's a 'shortcut' to setting some Properties directly after initialization.
Consider this:

C#

// Instead of doing:
Person p = new Person();
p.Name = "Naerling";
p.LastName = "Hell yeah!";
p.Age = 24;
// Or...
Person p = new Person() { Name = "Naerling", LastName = "Hell yeah!", Age = 24 };
// And then...
this.AddPersonToPhoneBook(p);

// You could be doing:
this.AddPersonToPhoneBook(new Person() { Name = "Naerling", LastName = "Hell yeah!", Age = 24 });

Personally I never use this syntax. I have no good reason not to though.

Posted 30-Jan-12 11:22am

Sander Rossel

Comments

Sergey Alexandrovich Kryukov 30-Jan-12 17:25pm

Correct, my 5.
About use or not -- please see my answer (why not?).
--SA

Sander Rossel 30-Jan-12 17:31pm

Thanks :)

Espen Harlinn 30-Jan-12 17:25pm

5'ed! :)

Sander Rossel 30-Jan-12 17:31pm

Thanks! :)

Sergey Alexandrovich Kryukov 30-Jan-12 17:26pm

What I really like is the possibility to add ',' after the last element (same in array initializers). It really improves maintenance.
--SA

Sander Rossel 30-Jan-12 17:31pm

Never noticed that! Wouldn't know why that's possible... Except that if you'd ever add a Property you'd already have the , which might really come in handy if you're in a hurry!

Sergey Alexandrovich Kryukov 30-Jan-12 17:37pm

Not even in a hurry. It makes editing more smooth, cause less mistakes.
There was a long-lasting competition between separator-not-terminator syntax (Pascal, which is much stronger in many aspects of syntax compared with C, but not in this aspect) and terminator-not-separator (C/C++, but by some reason only for ';' in statements). Finally we have nearly optimal syntax.
--SA

Sander Rossel 30-Jan-12 17:44pm

Not sure I understand... I'm a VB programmer, we don't have terminators :)
So why would I create an array like this:
int[] i = new[] {1, 2, 3, 4,}; // Notice the , at the end.
instead of
int[] i = new[] {1, 2, 3, 4};
If I would never need to edit this I would just add 5 to the first one and , 5 to the last one...

Sergey Alexandrovich Kryukov 30-Jan-12 18:28pm

I don't leave in California, so we also don't have Terminators!

First, of all, a little fix to you answer: "Shortcut for setting some Properties". And Fields, too. Even though non-private fields are not recommended, they can be used, too.

Now, here is the reason. This is nothing but pure support during editing.

You have:
{
A,
B,
C,
}
To shuffle C into different position or add D, you only shuffle lines or add a line. I last comma was not allowed, you also needed to add one comma and add another one. Cumbersome. Same thing -- in one line. Easier to edit, all members are identical. Easier to generate code.

--SA

Sander Rossel 30-Jan-12 18:41pm

Ah, that makes sense.
It's the reason why I put the comma in front of any fields in select or update statements in SQL :)

select
id
,name
,lastname
from person
Now if I want to add age or delete lastname I only need to edit one row :)
Thanks for the example!