Sorry for this stupid question, but I can't find answer for it. So, why I can't write code like this in C#:
int a = 10, b = 20, c = 30, d = 40; a = b, c = d; In C++ I can write it and it will be ok.
Why it doesn't compile in C#?
3 Answers
You can write the first line. That is allowed in C#, and spelled out in section 8.5.1 of the C# Language Spec, where it shows that each local-variable-declarator can be in a list that's comma separated:
local-variable-declarators: local-variable-declarator local-variable-declarators , local-variable-declarator However, C# does not have a comma operator like C++, so you have to split the second line:
int a = 10, b = 20, c = 30, d = 40; a = b; c = d; 
4 Comments
Nikita Sivukhin
Can you explain, what mean comma operator in C#? Why i can initializate varibale by comma, write statements in for but can't write such code?
Reed Copsey
@NikitaSivukhin There is no comma operator in C#. The only reason that's legal in C++ is that there is an operator in that language which allows multiple expressions to be placed where a single expression is expected (the C++ comma operator). That operator doesn't exist in C# - it's just not part of the language.
Nikita Sivukhin
Why i can write i = x, j = y in this code:
for (int i = 0, j = 0;; i = x, j = y) {...} This is special design for "for"?Reed Copsey
@NikitaSivukhin Yes - For loops allow a "statement-expression-list" (the list is key) in C#.
Simply because C# is not C++, and the two languages are different from one another.
Or, more precisely: The C# language is not a superset of the C++ language. Therefore not every C++ program is a valid C# program.
answered Sep 19, 2014 at 19:02
stakx - no longer contributing
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Comments
The first line is just fine. However, the second line consists of two separate statements. Statements have to be separated by a semicolon ;.
int a = b, c = d;if you want to get rid off of the values of a and c?