C#'s sneaky typedef

Super Lloyd

Awesome! Can you some other creating stuff? like. I dunno...

using int = System.String;

?! :P

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Lost User

No you can't just throw any keyword in there, it has to be a contextual keyword that isn't a keyword in that context. For example:

using from = System.SByte;
using let = System.Byte;
using orderby = System.Single;
using select = System.String;

Thomas Daniels

And this also works:

using System;
...
using String = System.Int32;

And:

String s = "str"; // throws an error
String s1 = 5; // this doesn't throw an error

The quick red ProgramFOX jumps right over the Lazy<Dog>. My latest article: Understand how bitwise operators work (C# and VB.NET examples) My group: C# Programmers Group

Lost User

String is not a keyword, so that's not very surprising..

Oshtri Deka

A bit dramatic, but generally I agree.

Mislim, dakle jeo sam.

Gary Wheeler

Precisely my initial reaction. Their head should be mounted on a pike outside the cube farm's walls as a warning to others.

Software Zen: delete this;

KP Lee

I kind of had your first responder's reaction to this code, then recalled my irritation with code that used var and forced me to look-up the return type of the function to figure out what the object was. So, my second reaction was YA, someone is forcing the lazy programmer to stop using the lazy var keyword. I want to kill 'm and sing his/her praises. You could say I'm conflicted.

KP Lee

harold aptroot wrote:

String is not a keyword, so that's not very surprising..

Agreed. My first reaction too.

BobJanova

If it was the second then they should have linked it to a class called DoNotUseVar or something.

KP Lee

BobJanova wrote:

they should have linked it to a class called DoNotUseVar or something.

:laugh: The casting error would certainly pop out better. Less confusing than the unsuspected error generated by:

byte a = 10;
var b = a;
byte c = b;

Simon ORiordan from UK

I haven't used var except where essential in almost 10 years. :-D

BobJanova

I don't like it except in type declaration plus initialise statements ... there's no point doubling up the type information in

var dict = new Dictionary<String, IList<DataColumn>>();

But of course one of the places you can't use it is in field declarations which is where you want to do that a lot! It's also a bit ugly writing code that saves a Linq query if you declare the type (IQueryable<T>, right?). It seems to be standard to use var there, although I've been known to put the actual type instead.

Lutoslaw

BobJanova wrote:

var dict = new Dictionary<String, IList<DataColumn>>();

var columnNameDict = new Dictionary>();

FTFY Just to ensure that nobody use your dict to find a way to a cathouse. Or something like that. BTW. I'd like to have this syntax:

Dictionary<String, IList<DataColumn>> dict = new();

I'd have information on type in a more logical place and could concentrate on parameters passed to a constructor. And still no doubling.

Greetings - Jacek

BobJanova

Yes fair point with the name there. I'd like a type syntax like that (well maybe not exactly like that, it looks a bit weird, but similar) as well, but since we don't and we do have var, it deputises quite well.

Lost User

Looks nice, but violates the (already violated) rule that the type of an expression is determined by its parts, not by the context in which it appears. Of course that rule is already broken by integer constants.. and null cheats with its "null type" that is implicitly convertible to many types. So I don't know.

BobJanova

I don't think that's really a rule any more. What's the type of the lambda x => x + 1? You can't tell without looking at the calling context.

Lost User

It's still a rule, it just doesn't apply everywhere. The situation for lambda's is particularly bad[^], but that's no excuse to infect the rest of language with such nonsense.

AspDotNetDev

Why 10 years? Var was introduced with C# 3.0, which was released about 6 years ago. I hope you weren't trying to use it before then. :doh:

Thou mewling ill-breeding pignut!

Chad3F

Seems about the same as doing this in C or C++: /* What could possibly go wrong */ #define int double Since the substitutions are done before the tokens are interpreted.

KP Lee

Simon O'Riordan from UK wrote:

I haven't used var except where essential in almost 10 years.

Wow, you must be really advanced. When I took C# training in 2005 var never came up and I read the manuals from cover to cover and never saw the command. I was under the impression it was introduced in 2005. (I can easily be totally wrong about that.) When is it ever essential? There is always:

object x = ...