There is a way to pass-by-reference using variable parameters in C#?

Question

I would like to have a function that modifies some variable list of parameters but they are all value types (int, string). There is a way to make the params keyword work with ref keyword or something close to that?

public void funcParams(params object[] list)
{
   /* Make something here to change 'a', 'b' and 'c' */
}

public void testParams()
{
    int a = 1, b = 2, c = 3;

    funcParams(a, b, c);
}

The problem is, I'm trying to make my life easier making a method that modifies the object fields. I'm doing some dynamic code generation using Cecil and I'm trying to avoid writing too much IL generated code.

To simplify I would like to pass the list of fields by reference I need to change to a function that changes them instead of changing them by generating the respective IL. Some of the parameters are nullable and make the code generation a little more painful. Making some overload methods instead of params won't be much useful in this case.

Answer 1

Well, you could declare a few overloads, i.e.

public void FuncParams(ref int a) {...}
public void FuncParams(ref int a, ref int b) {...}

etc

Otherwise, you'll have to read back from the array (as params really means "implicit array"):

object[] args = {1,2,3};
funcParams(args);
Console.WriteLine(args[0]); // updated
Console.WriteLine(args[1]); // updated
Console.WriteLine(args[2]); // updated

(of course, if it only accepts ints, it would be better to use an int[] throughout)

Answer 2

Yes. It is possible.

However, the resulting code is "unsafe" which makes it unverifiable.

That may or may not be an issue depending on your requirements.

In any case, here is the code:

using System;

namespace unsafeTest
{
    class MainClass
    {
        public static void Main(string[] args)
        {
            Console.WriteLine("Hello World!");
            unsafe 
            {       
                int x = 0;
                int y = 0;
                int z = 0;
                bar(&x, &y, &z);
                Console.WriteLine(x);
                Console.WriteLine(y);
                Console.WriteLine(z);
            }
        }

        unsafe static void bar(params int *[] pInts)
        {
            int i = 0;
            foreach (var pInt in pInts)
            {
                *pInt = i++;
            }
        }
    }
}