Passing an interface type by reference?

[overwraith]

So, I wrote some code for appending to an array, and I thought to myself, would be cool to make the method more generic using an interface. I keep getting this error though that basically says that the compiler's best overloaded method that can match this is _____, and it does not like how I am passing it. So I am getting the distinct impression that interfaces cannot be passed by reference. Here is the code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Test2 {
    class Program {
        static void Main(string[] args) {
            MyClass[] mine = new MyClass[5];

            for (int i = 0; i < mine.Length; i++)
                mine[i] = new MyClass(i);

            foreach (MyClass temp in mine)
                Console.WriteLine(temp.ToString());

            appendIComparable(ref mine, ref new MyClass(8) );

            foreach(MyClass temp in mine)
                Console.WriteLine(temp.ToString());

            pause();

        }

        public static void pause() {
            Console.Write("Press any key to continue... ");
            Console.ReadLine();
        }

        public class MyClass : IComparable {
            public int i;

            public MyClass(int i) { this.i = i; }

            public int CompareTo(object obj) {
                if (obj == null) return 1;

                MyClass otherClass = obj as MyClass;
                if (otherClass != null)
                    return this.i.CompareTo(otherClass.i);
                else
                    throw new ArgumentException("Object is not my class... ");
            }

            public override string ToString() {
                return i.ToString();
            }

        }

        public static void appendIComparable(ref IComparable[] original, ref IComparable append) {

            //move original from one array to the other
            int j = 0;
            IComparable[] newArray = new IComparable[original.Length + 1];
            for (; j < original.Length; j++) {
                if (original[j].CompareTo(append) > 0) {//if the append customer is larger than the current customer in the first list
                    j++;
                    break;
                }
                else
                    newArray[j] = original[j];
            }

            newArray[j] = append;//then add the append customer to the list

            for (; j < original.Length; j++)//and then finish up appending the customers from the first list to the end list
                newArray[j] = original[j - 1];

            append = null;

            original = newArray;
        }//end method
    }//end class
}//end namespace

So am I wrong, or is this just not possible. Also, was for a customer comparison method before, so comments don't quite match up.

[Ketsuekiame]

Firstly, although MyClass inherits IComparable the compiler doesn't know that it can be converted (sometimes the compiler is dumb). If you change your original definition from MyClass[] mine = new MyClass[5] to IComparible[] mine = new MyClass[5] that will be fine.

Finally, you can only pass an assignable value with the explicit ref keyword. new MyClass(8) isn't assignable, you would need to put this into a variable first and then pass it through.

Strictly speaking, however, you can drop the ref keyword. Your object is being passed by reference anyway.

For Completeness:

When you pass an array into a method, you're passing the pointer to it by value. What this means is that any changes to the contents of the array will be reflected in the original object, however, re-assigning the array will not. That's why you needed the ref keyword. You don't need the ref keyword on the second parameter as it is already passed by reference.

[overwraith]

That was very helpful, thanks.