Replacer.cs

using Microsoft.VisualBasic.FileIO;
using System.IO;

namespace ReplaceIcon
{
    public class Replacer
    {
        public void Replace(ThemeIcon current, ThemeIcon replacement)
        {
            foreach (var size in current.Sizes)
            {
                Recycle(current[size]); // move an icon to recycle bin (trash)

                foreach (var related in size.Related)
                {
                    if (File.Exists(replacement[related]))
                    {
                        // TODO: if it's a symbol link make sure it will replace an icon, not the symbol link
                        Copy(replacement[related], current[size]);

                        break;
                    }
                }
            }
        }

        public void Copy(string source, string destination)
        {
            if (File.Exists(source))
                File.Copy(source, destination);
        }

        public void Recycle(string icon)
        {
            if (File.Exists(icon))
                FileSystem.DeleteFile(icon, UIOption.OnlyErrorDialogs, RecycleOption.SendToRecycleBin);
        }
    }
}