C# GZip Compress DeCompress

using system;
using system.collections.generic;
using system.linq;
using system.text;
using system.threading.tasks;
using system.io.compression;
using system.io;
using system.diagnostics;

namespace consoleapp1
{
    class program
    {
        static void main(string[] args)
        {
            decompressdemo();
            console.readline();
        }                
        
        private static void compressdemo()
        {
            string source = @"d:\";
            string[] files = directory.getfiles(source, "*", searchoption.alldirectories);
            if(files!=null && files.any())
            {
                foreach(var file in files)
                {
                    compressfile(file);
                }
            }                              
        }
        private static void compressfile(string file)
        {
            console.writeline($"start to compress {file}");
            stopwatch sw = new stopwatch();
            sw.start();
            string compressedfullname = path.combine(path.getdirectoryname(file), path.getfilenamewithoutextension(file)) + ".zip";
            if (file.exists(compressedfullname))
            {
                file.delete(compressedfullname);
            }

            task compresstask = task.run(() =>
            {
                using (filestream fs = file.open(file, filemode.open))
                {
                    using (filestream compressedfilestream = file.create(compressedfullname))
                    {
                        using (gzipstream gzipstream = new gzipstream(compressedfilestream, compressionmode.compress))
                        {
                            fs.copyto(gzipstream);
                        }
                    }
                }
            });

            compresstask.wait();
            sw.stop();
            if (compresstask.iscompleted)
            {
                console.writeline($"{file} has been compressed successfully,cost:{sw.elapsedmilliseconds} elapsedmilliseconds!");
            }
        }
        private static void decompressdemo()
        {
            string source = @"d:\";
            string[] compressedfiles = directory.getfiles(source, "*.zip");
            if (compressedfiles != null && compressedfiles.any())
            {
                foreach (var file in compressedfiles)
                {
                    decompressfile(file);
                }
            }
        }
        private static void decompressfile(string file)
        {
            console.writeline($"start to decompress {file}");
            stopwatch decompresssw = new stopwatch();
            decompresssw.start();

            string newfilename = path.combine(path.getdirectoryname(file)) + guid.newguid().tostring() + path.getfilenamewithoutextension(file);

            task decompresstask = task.run(() =>
            {                
                using (filestream fs = file.open(file, filemode.open))
                {
                    using (filestream decompressedstream = file.create(newfilename))
                    {
                        using (gzipstream gzipdecompressedstream = new gzipstream(fs, compressionmode.decompress))
                        {
                            gzipdecompressedstream.copyto(decompressedstream);
                        }
                    }
                }
            });

            decompresstask.wait();
            if(decompresstask.iscompleted)
            {
                decompresssw.stop();
                console.writeline($"decompress as {newfilename} cost {decompresssw.elapsedmilliseconds} milliseconds");
            }           
        }
    }
}