Question

I have a typed array MyType[] types;
and i want to make and independant copy of this array. i tried this

MyType[] types2 = new MyType[types.Length] ;

types2 = types ;

but this create a reference to the first. I then tried

Array.Copy( types , types2 , types.Length ) ;

but I have the same problem: changing a value in the first array changes the value in the copy as well.

How can I make a completely independent or deep copy of an Array, IList or IEnumerable?

Answer 1

Implement a clone method on MyType, using protected method MemberwiseClone (performs shallow copy) or using a deep cloning technique. You can have it implement an ICloneable then write several extensions methods that will clone the corresponsing collection.

interface ICloneable<T>
{
    T Clone();
}

public static class Extensions
{
    public static T[] Clone<T>(this T[] array) where T : ICloneable<T>
    {
        var newArray = new T[array.Length];
        for (var i = 0; i < array.Length; i++)
            newArray[i] = array[i].Clone();
        return newArray;
    }
    public static IEnumerable<T> Clone<T>(this IEnumerable<T> items) where T : ICloneable<T>
    {
        foreach (var item in items)
            yield return item.Clone();
    }
}

You must do this because while a new array is created when you use Array.Copy it copies the references, not the objects referenced. Each type is responsible for copying itself.