Are immutable arrays possible in .NET?

Is it possible to somehow mark a System.Array as immutable. When put behind a public-get/private-set they can't be added to, since it requires re-allocation and re-assignment, but a consumer can still set any subscript they wish:

public class Immy
{
    public string[] { get; private set; }
}

I thought the readonly keyword might do the trick, but no such luck.

Yes, You can now use ImmutableArray with .NET Core 1.0+

using System.Collections.Immutable;

var arr1 = new [] {1,2,3}.ToImmutableArray();
var arr2 = ImmutableArray.Create(new [] {1,2,3});

Demo in DotNetFiddle

See Also: Please welcome ImmutableArray by Immo Landwerth