CODEWITHSUNDEEP
c#.netc#-4.0
Samidjo
Samidjo

Reputation: 2355

Is there a performance difference between int i =0 and int i = default(int)?

I was creating an integer and i wanted to instantiate it with 0 before working with.

I wrote firstly

int i = default(int);

then i removed it to replace with the other one which is

int i = 0;

I would like to know if my choice is the best in mini mini performance. Will the default() function increase the instructions at compile time?

Upvotes: 5

Views: 1571

Answers (3)

JakeJ
JakeJ

Reputation: 1381

The only real difference that it will make is the compile-time, so I suppose it would be a milli-milli-milli-milli second faster one way than the other when you press Debug or Compile but as soon as it's compiled, it will be exactly the same as Marlon said

These small changes will only affect your actual programming time so in a broader sense of the term, writing out default(int) is slower than writing 0 and the time you put thought into it took even longer.

Upvotes: 1

Adam Maras
Adam Maras

Reputation: 26863

Marlon's answer is technically correct, but there should be a clear semantic difference between each option.

int i = 0;

Initializing to literal zero makes semantic sense when you want to do a mathematical operation on the integer, and that operation needs to start with the variable being the specific value of zero. A good example would be creating an index counter variable; you want to start with zero and count up.

int i = default(int);

Setting a variable to its default value makes sense when you're, for example, creating a class with said variable where you know the variable will be manually set later on in the process. Here's an example (however impractical it may be):

class IntegerClass
{
    private int value;

    public IntegerClass(int value)
    {
        this.value = value;
    }

    public void Reset()
    {
        this.value = default(int);
    }
}

Again, they're technically equal (and in fact will compile to identical CIL) but each provides a different semantic meaning.

Also, using default could be required to initialize a variable when using generics.

public T SomeOperation<T>()
{
    T value = default(T);

    this.SomeOtherOperation(ref value);

    return T;
}

Upvotes: 4

Marlon
Marlon

Reputation: 20312

No, they are resolved at compile time and produce the same IL. Value types will be 0 (or false if you have a bool, but that's still 0) and reference types are null.

Upvotes: 13

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