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Hay I didn't know even If this question has asked before but my problem is as following.
In my c# console application I had declared a variable i with assigning a value as int i = 0 and now I want increment i by 2, obviously I can use following cede.

int i = o;
i += 2;
Console.WriteLine(i); 
Console.ReadLine(); 
//OUTPUT WILL BE 2

but this one is my alternate solution. As my lazy behavior I refuse to use this code and I had used following code.

int i = 0;
i += i++;
Console.WriteLine(i);
Console.ReadLine();

In above code I had accepted FIRST i++ will increment by one and than after it will again increment by i+=i but this thing is not happen.!!!
I doesn't know why this thing is happening may be I had done something wrong or some compilation problem.????? Can any one suggest me why this happening???? I just want to know why code no 2 is not working? what is happening in there?

Sagar Upadhyay
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  • This has been answered here a few times, basically i++ increments i **after** assigning the value. If you want you can use ++i to increment before: `ì += ++i;` [here](http://stackoverflow.com/questions/24853/what-is-the-difference-between-i-and-i)'s your question answered in more detail. – gaynorvader Dec 05 '12 at 15:49
  • you could also try i = i+2; – Daniel Lane Dec 05 '12 at 15:51

3 Answers3

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The i++ returns the value of i (0) and then adds 1. i++ is called post-increment.

What you are after is ++i, which will first increase by one and then return the increased number.

(see http://msdn.microsoft.com/en-us/library/aa691363(v=vs.71).aspx for details about increment operators)

Tomas Grosup
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  • Ya i know this but threw my logic it should increment by 2, my question is that what is happening or what is wrong in my code no 2? Why it do not give me ans = 2? – Sagar Upadhyay Dec 05 '12 at 15:53
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i needs to start off with 1 to make this work.

int i = 1;

EDIT::

int i = 0;
i += i++;

Your code above expresses the following:

i + 0 then add one

if you use i += ++i; then you'll get i + 1 as it processed the increment beforehand.

Sandeep Bansal
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  • Ya i know this but threw my logic it should increment by 2, my question is that what is happening or what is wrong in my code no 2? Why it do not give me ans = 2? – Sagar Upadhyay Dec 05 '12 at 15:52
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What your code is doing:

  • "i++" is evaluated. The value of "i++" is the value of i before the increment happens.
  • As part of the evaluation of "i++", i is incremented by one. Now i has the value of 1;
  • The assignment is executed. i is assigned the value of "i++", which is the value of i before the increment - that is, 0.

That is, "i = i++" roughly translates to

int oldValue = i; 
i = i + 1 
//is the same thing as 
i = oldValue;

The post-increment operator increments the value of your integer "i" after the execution of your i++

For your information:

 i++ will increment the value of i, but return the pre-incremented value.
 ++i will increment the value of i, and then return the incremented value.

so the best way of doing the 2 step increment is like that:

i +=2
TrizZz
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