How to pass an integer "pointer" from C# to managed CLI C++

Question

This should be easy (and it is in C++) but I cannot find the right syntax to perform the following task:

In C# I have an integer 'result' that I want to pass to a managed C++ function.
In the managed C++ function I set the value 'result' to say, 6.
When the function returns, I have the set value in C# now as 6.

(The code segment I copy in using the enter code tool above is so ugly I can't warrant its use.)

In C++ all I need is to use an integer pointer, pass the pointer to the function, have the function set it, and then I have the set value in the caller. I would really appreciate it if someone could write a little code snippet in C# that takes an integer and somehow passes it as a pointer by boxing or whatever to a managed function and have the managed function set the value so the C# caller has the value on return (but not as a return value). Matching the syntaxes in the C# world with the analog in the managed C++ world is half the battle.

I can't even figure out a good way to word this question in a google search.

"Reference parameters", and the similar "output parameters", would be the term for which to Google. — Lance U. Matthews
– Lance U. Matthews, Commented Apr 27, 2013 at 0:39

Hans Passant · Accepted Answer · 2023-06-04 07:53:23Z

2

Simply pass the argument by reference:

public ref class Example {
public:
    static void Foo(int% arg) {
        arg = 42;
    }
};

Then you call it from C# with:

int value = 0;
Example.Foo(ref value);

And don't forget that you can return a value from a method as well.

edited Jun 4, 2023 at 7:53

answered Apr 27, 2013 at 0:37

Hans Passant

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1 Comment

Brian Reinhold Over a year ago

Bless you! Worked like a charm. Yes I know I can return a value but in my case I am already returning something else so the position is filled!

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