please explain if there is any difference between int a; and int a =new int()

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hi expert

Is there any difference between following statement in C#?

int a;

int a=new int();

please explain.

Thanks & Regards
Divaker

Posted 2-Jul-13 23:43pm

Divaker @ Emerging Programmer

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3 solutions

Solution 3

VB

int a;: allocates an int on stack and does not initialize it.
int a=5;: allocates an int on stack and sets it to 5;
int a=new int();: allocates an int on stack and sets it to 0;
int a=new int(5);: does not compile.

OR

As you can see second one just initialize it and first one initialize and set . As for the IL code generated, they both get initialized in a single line

Posted 2-Jul-13 23:55pm

ErBhati

Updated 2-Jul-13 23:58pm

v2

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CPallini · Accepted Answer · 2013-07-02T23:55:00

Solution 2

The line

int a;

declares the int variable a. It must be initialized before use.

The line

int a=new int();

declares and initialize to 0 the int variable a.

See Value Types (C# Reference)[^].

Posted 2-Jul-13 23:55pm

CPallini

Comments

Divaker @ Emerging Programmer 3-Jul-13 6:10am

Hi Cpallini,

you provided a great link.
but here is an explanation

myInt = new int(); // Invoke default constructor for int type.

it may be i am behaving like a kid. yes i am a fresher.

if there is constructor, then there will be a class

and i have read class is reference type. then how int a =new int(). react as value type. means how and why the memory allocated into stack?

CPallini 3-Jul-13 8:01am

It is not a class, it is a value type. Value types may have constructors too, see, for instance:
http://msdn.microsoft.com/en-us/library/ah19swz4.aspx

V. · Accepted Answer · 2013-07-02T23:54:00

See here[^]

my guess is that new int() will generate a 0 and int a (without new) will generate some weird value like int max or int min values.

Create a console application and try to print it out.

C#

class Program {
    static void Main(string[] args) {
        int a;
        int b = new int();
        Console.WriteLine("a = " + a);
        Console.WriteLine("b = " + b);
        Console.ReadLine();
    }
}

Just tried it, doesn't even compile. a is uninitialized so you can't use it. You need to set a value before using a.