Question

My question is related to C# function parameters. I’m used to C++ where parameters are values by default unless you explicitly specify them as references. So, in C#, how do I make function parameters to be passed by value instead of by reference? Actually, I just want to know how to pass a variable, and not have that variable modified after the call to the function.

E.g:

void foo(Widget w)
{
     w.X = 3;//where w wouldn't really be modified here
}

Answer 1

As int is a primitive data type, x is already passed by value in your older example.

Proof of concept:

class Program
{
    static void Main(string[] args)
    {
        int x = 1;
        System.Console.WriteLine(x); // 1

        foo(x);
        System.Console.WriteLine(x); // 1
    }

    static void foo(int x)
    {
        x++;
    }
}

EDIT: for non-primitive data types, the answers to this question state that C# doesn’t implement copy constructors like C++ does, so I’m not sure of a way to pass actual objects by value, other than making your class implement the ICloneable interface or something. (For the record, C# passes references to objects by value.)

EDIT 2: Mark Rushakoff’s answer is an excellent, if not the best, way to go… assuming your Widget type is defined by you (it looks so).