c# var

ZurdoDev

What is the love affair with var? I see sample code where they do something like

This feels lazy to me but I am open minded and am curious if I am missing something. Is there some benefit to declaring most things var instead of what they actually are? In the case above, a string.

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F ES Sitecore

The only benefit is that if you don't understand types then there is a chance your code will work using var even though you don't know why. Also I've found some common style tools dictate you should use var. I don't mind it for

var name = "Blah";

or

var people = new List();

but I hate it when people use it for things like

var data = SomeFunction();

Marc Clifton

ZurdoDev wrote:

This feels lazy to me but I am open minded and am curious if I am missing something. Is there some benefit to declaring most things var instead of what they actually are? In the case above, a string.

I felt the same way initially, and I agree, for something simple like a native type, I rarely use var. However: var complicatedDictionary = new Dictionary>(); and worse, I like definitely like it.

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GuyThiebaut

The advantage of var is if "http://someapi" was a variable or class instance instead of a string literal and you changed its type, you would not then need to refactor the code elsewhere. In your example it's just a case of habit probably, however it's obvious from what is on the right that it's a string. It can sometimes make it harder to debug issues as jumping to the class definition might not always be supported in the IDE you use to debug the var url value with or have to wait for the IDE to resolve the type that the var is. That's my take on var...

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Greg Utas

I use auto, the C++ equivalent, whenever it will deduce the correct type. - It forces you to initialize the variable. - If the variable is initialized by calling a function, and that function's return type changes, the code might not even be affected. - Some type names are long or complicated, and I hate spilling lines. Some argue that it makes the code harder to understand because the reader has to figure out the type. My counterargument is that the reader doesn't understand how the code fits into the system if this is the case.

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Slacker007

it is good for a lot of applications but can be missused very easily. it's main purpose is code readability.

MyMostExcellentBaseClassOfAllClassesInTheWholeWorld myClass = new MyMostExcellentBaseClassOfAllClassesInTheWholeWorld();

or

var myClass = new MyMostExcellentBaseClassOfAllClassesInTheWholeWorld();

It is really good when working with Linq, etc. as well.

ZurdoDev

Marc Clifton wrote:

var complicatedDictionary = new Dictionary<SomeKey, List<KeyValue>>(); and worse, I like definitely like it.

I can see that.

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OriginalGriff

I'd actually prefer it is you could do this:

Dictionary> complicatedDictionary = new *();

To me, that would be a more natural way of showing what the type of complicatedDictionary actually is. As it is, I find var is mainly over used by the lazy-and-don't-care script kiddies ...

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OriginalGriff

I'd rather see it as:

MyMostExcellentBaseClassOfAllClassesInTheWholeWorld myClass = new *();

If that was possible.

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Lost User

var is ok as long as I can have a look to the code in VS with the help of intelisense. But in case I study a code snippet on www it becomes simply horrible because the real type is something hidden :(

It does not solve my Problem, but it answers my question

Johnny J

I think you can find instructions on how to create your own programming language here on CP, actually... ;P

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obermd

As far as I can tell most uses of "var" are sheer laziness. The only time I var useful is when I need to store the results of a LINQ expression for later processing.

obermd

GuyThiebaut wrote:

The advantage of var is if "http://someapi" was a variable or class instance instead of a string literal and you changed its type, you would not then need to refactor the code elsewhere.

Absolutely not true. Changing a data type and then attempting to use it elsewhere is guaranteed to cause you to have to modify code everywhere it's used. Fortunately the VS IDE is smart enough to identify those spots for you.

obermd

This is one place where VB has a better syntax:

dim complicatedDictionary as New Dictionary(of SomeKey, List(KeyValue))

I'd prefer to see the < and > symbols used around the type information as this would make it clear what is type information vs. New parameters/arguments.

GuyThiebaut

obermd wrote:

Absolutely not true. Changing a data type and then attempting to use it elsewhere is guaranteed to cause you to have to modify code everywhere it's used.

Even when changing from a short to a long?

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Wendelius

I rarely use var but I do use it when returning a tuple from a method to avoid out parameters. For example

void MainMethod() {
...
var methodCall = SomeMethod();
if (!methodCall.Success) {
return;
}
...
}

(bool Success, int? ReturnValue) SomeMethod() {
int? retValue;

...
if (...) {
return (Success: false, ReturnValue: null);
}
...

return (Success: true, ReturnValue: retValue):
}

Richard Deeming

That should hopefully be coming in C# 9: csharplang/target-typed-new.md at master · dotnet/csharplang · GitHub[^] Champion "Target-typed `new` expression" · Issue #100 · dotnet/csharplang · GitHub[^] Edit: As already mentioned in the Insider News[^]. :)

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Richard Deeming

Or better yet:

var (Success, ReturnValue) = SomeMethod();
if (!Success) {
return;
}

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OriginalGriff

Hah! I just spent half an hour trying to persuade Google to let me know how you make suggestions for the C# spec ... :laugh: That language change I will use!

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Pete OHanlon

Ah, the use of var. I know that some people use var to do code alignment on variable names; the idea being that it's easier to scan the name if it lines up.

private void DoSomething()
{
var apiEndpoint = new Uri("http://someapi");
var retryCount = 10;
var longClassName = new ThisIsAReallyLongNameThatWouldReallyScrewUpTheClassNameDeclaration();
// body of the method.
}

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