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class Test
 int KT(int a)
   if (a > 0) return 0;
   else return a + NT(ref a); //-5 + nt

 int NT(ref int a)
   if (a < 0) return a++; //-5+1 = -4
   else return a * a;

 static void Main()
   Test Obj = new Test();

Why answer is 10??

What I have tried:

Why answer is 10?
What is Explain how the code works
Updated 18-Sep-22 23:17pm

With the Postfix and Prefix operators the sequence of operations is the same apart from the returned value.

//return undated value
return incrementedVal;

//return original value
return temp;

So the original value of a is returned by your NT method.
The reason that int a does not get updated is because it is passed to your method by value. For it to be updated, pass it by reference. Something like.
public int KT(ref int a)
   //use the Ternary operator to avoid 'if' 'else'
   return a > 0 ? 0 : a + NT(ref a);
 //use expression syntax to get the definition down to a single line
 //public int KT(ref int a) => a > 0 ? 0 : a + NT(ref a);

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To add to what FreedMalloc has rightly said, I'll add this "solution" to get the link to you.

Have a look here: Why Does x = ++x + x++ Give Me the Wrong Answer?[^] - it explains what postfix operations do, and why you have to be very careful with them.
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FreedMalloc 19-Sep-22 0:47am    
Yes. I couldn't remember the name of this article. I should have have thought to peruse your list. It too is worth a 5.
First off, what OriginalGriff stated above in the Solution 1 is very good advice.
Use the debugger! It is your greatest coding tool!
Take it from someone who has worked on systems without one!

Here's a hint for you. Pay special attention to the first line in the method NT.
You need to answer the question: What exactly will "return a++;" do?

Review how the postfix operator++ works.

BTW, the output result is NOT 10 as you state. Look a little closer.
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OriginalGriff 19-Sep-22 0:34am    
Take a five!
Malek Alshorbaji 19-Sep-22 16:32pm    
The answer in virtual studio is -10
FreedMalloc 19-Sep-22 16:45pm    
Yes, it's -10. Do you understand why it's -10 and not -9?
If not, read the link in Solution 3 posted by OriginalGriff.
The postfix and prefix operators can be a bit tricky sometimes.
Do you have any idea how much work explaining code line by line is?
Every single line needs a paragraph of explanation! For example:
int next = r.Next();

Create a new variable called "next" which can hold a integer value. From the previously declared Random instance "r", call the "Next" method to get a new random number, and assign it to the "next" variable.

Can you imagine how long it would take us to explain even a very short code fragment like your example, line by line?

No. It is not going to happen. If you have a specific problem, then ask a question about it. But think first - would you want to sit down for 45 minutes and type up a line-by-line description for no good reason?

You don't understand how code you didn't write works? use the debugger and watch what happens while it is running.
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