Umbraco-CMS/src/Umbraco.Core/IO/FileSystemExtensions.cs

using System;
using System.IO;

namespace Umbraco.Core.IO
{
    public static class FileSystemExtensions
    {
        public static long GetSize(this IFileSystem fs, string path)
        {
            using (var file = fs.OpenFile(path))
            {
                using (var sr = new StreamReader(file))
                {
                    var str = sr.ReadToEnd();
                    return str.Length;
                }
            }
        }

        public static void CopyFile(this IFileSystem fs, string path, string newPath)
        {
            using (var stream = fs.OpenFile(path))
            {
                fs.AddFile(newPath, stream);
            }
        }

        public static string GetExtension(this IFileSystem fs, string path)
        {
            return Path.GetExtension(fs.GetFullPath(path));
        }

        public static string GetFileName(this IFileSystem fs, string path)
        {
            return Path.GetFileName(fs.GetFullPath(path));
        }

        //TODO: Currently this is the only way to do this
        internal static void CreateFolder(this IFileSystem fs, string folderPath)
        {
            var path = fs.GetRelativePath(folderPath);
            var tempFile = Path.Combine(path, Guid.NewGuid().ToString("N") + ".tmp");
            using (var s = new MemoryStream())
            {
                fs.AddFile(tempFile, s);
            }
            fs.DeleteFile(tempFile);
        }
    }
}