What's happening with this expression? b = a + (a = a + 5)

Question

a = 5
b = a + (a = a + 5)

result b = 15

Why the first \'a\' do not changes after that (a = a + 5)? But why second one changes? What exactly is

Answer 1

Unlike C and C++, the order of evaluation of subexpressions are left to right in C#. That's why the expression

j= ++i + ++i ;   

has well defined behavior in C# while undefined in C and C++.

In expression

b = a + (a = a + 5)  

left a will be evaluated first, then a+5 is evaluated and assigned to a and after addition of both evaluated subexpression, b will have value 15.