0

Is it okay to do

new Class().Methodname()

when I don't need the object anymore, or is it better to do

var class = new Class();
class.Methodname();
DudeWhoWantsToLearn
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    What is your definition of _better_? – Steve Nov 28 '19 at 14:30
  • The same definition like "What's better? Using string x = ""; or using String x = "";" Maybe the first way messes with the storage – DudeWhoWantsToLearn Nov 28 '19 at 14:31
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    They are both essentially the same thing, the only real difference is in the second example you are storing the reference to the object created whereas in the first you arent. The only reason to do the second would be if you wished to access other elements on the class object. If it is a method that is frequently called like this then it might be better changing it to a static method instead. – Christopher Townsend Nov 28 '19 at 14:31
  • If you can discard the newly created instance the moment the method completes, it would be better to design the method as a static method. If that's a library method you're calling, the library reeks like it is poorly designed. – Adwaenyth Nov 28 '19 at 14:45

3 Answers3

3

Is it okay to do

Well, that depends. Your program will work either way and the generated IL is (basically) identical when compiled for release. The question is, why is that method not static if it's apparently not dependent on any actual state of Class?

Generally, it's at least a good indication that the class is not modelled correctly if you find yourself creating a new instance and abandoning it directly afterwards only because you needed to call a method on it.

void Main()
{
    var x = new MyClass().Do();
    var z = new MyClass();
    var y = z.Do();
}

public class MyClass
{
    public string Do() => "hello";
}

Compiled under Release configuration, this results in the following IL:

IL_0000:  newobj      UserQuery+MyClass..ctor
IL_0005:  call        UserQuery+MyClass.Do
IL_000A:  pop         
IL_000B:  newobj      UserQuery+MyClass..ctor
IL_0010:  callvirt    UserQuery+MyClass.Do
IL_0015:  pop         
IL_0016:  ret       

MyClass.Do:
IL_0000:  ldstr       "hello"
IL_0005:  ret         

MyClass..ctor:
IL_0000:  ldarg.0     
IL_0001:  call        System.Object..ctor
IL_0006:  ret

For more information on the difference (call vs. callvirt), see e. g. this question.

germi
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0

I don't see much difference in between two approaches when it comes to performance .

Second approach gives you more readability and maintainability

Praveen M
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It depends. Like germi says it indicates a design flaw. But further, if the class implements idisposable you should be using it in the context of a try finally block or using:

using(var class = new Class())
{
   class.Methodname();
}

to make sure it is disposed and any resources it holds are released.

Kell
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