Use pure C# to extract .tar and .tar.gz files

ExtractTarGz.cs

using System;
using System.IO;
using System.IO.Compression;
using System.Text;

namespace TarExample
{
    public class Tar
    {
        /// <summary>
        /// Extracts a <i>.tar.gz</i> archive to the specified directory.
        /// </summary>
        /// <param name="filename">The <i>.tar.gz</i> to decompress and extract.</param>
        /// <param name="outputDir">Output directory to write the files.</param>
        public static void ExtractTarGz(string filename, string outputDir)
        {
            using (var stream = File.OpenRead(filename))
                ExtractTarGz(stream, outputDir);
        }

        /// <summary>
        /// Extracts a <i>.tar.gz</i> archive stream to the specified directory.
        /// </summary>
        /// <param name="stream">The <i>.tar.gz</i> to decompress and extract.</param>
        /// <param name="outputDir">Output directory to write the files.</param>
        public static void ExtractTarGz(Stream stream, string outputDir)
        {
            using (var gzip = new GZipStream(stream, CompressionMode.Decompress))
            {
                // removed convertation to MemoryStream
                ExtractTar(gzip, outputDir);
            }
        }

        /// <summary>
        /// Extractes a <c>tar</c> archive to the specified directory.
        /// </summary>
        /// <param name="filename">The <i>.tar</i> to extract.</param>
        /// <param name="outputDir">Output directory to write the files.</param>
        public static void ExtractTar(string filename, string outputDir)
        {
            using (var stream = File.OpenRead(filename))
                ExtractTar(stream, outputDir);
        }

        /// <summary>
        /// Extractes a <c>tar</c> archive to the specified directory.
        /// </summary>
        /// <param name="stream">The <i>.tar</i> to extract.</param>
        /// <param name="outputDir">Output directory to write the files.</param>
        public static void ExtractTar(Stream stream, string outputDir)
        {
            var buffer = new byte[100];
            // store current position here
            long pos = 0;
            while (true)
            {
                pos += stream.Read(buffer, 0, 100);
                var name = Encoding.ASCII.GetString(buffer).Trim('\0');
                if (String.IsNullOrWhiteSpace(name))
                    break;
                FakeSeekForward(stream, 24);
                pos += 24;

                pos += stream.Read(buffer, 0, 12);
                var size = Convert.ToInt64(Encoding.UTF8.GetString(buffer, 0, 12).Trim('\0').Trim(), 8);
                FakeSeekForward(stream, 376);
                pos += 376;

                var output = Path.Combine(outputDir, name);
                if (!Directory.Exists(Path.GetDirectoryName(output)))
                    Directory.CreateDirectory(Path.GetDirectoryName(output));
                if (!name.Equals("./", StringComparison.InvariantCulture))
                {
                    using (var str = File.Open(output, FileMode.OpenOrCreate, FileAccess.Write))
                    {
                        var buf = new byte[size];
                        pos += stream.Read(buf, 0, buf.Length);
                        str.Write(buf, 0, buf.Length);
                    }
                }

                var offset = (int)(512 - (pos % 512));
                if (offset == 512)
                    offset = 0;
                FakeSeekForward(stream, offset);
                pos += offset;
            }
        }

        private static void FakeSeekForward(Stream stream, int offset)
        {
            if (stream.CanSeek)
                stream.Seek(offset, SeekOrigin.Current);
            else
            {
                int bytesRead = 0;
                var buffer = new byte[offset];
                while (bytesRead < offset)
                {
                    int read = stream.Read(buffer, bytesRead, offset - bytesRead);
                    if (read == 0)
                        throw new EndOfStreamException();
                    bytesRead += read;
                }
            }
        }
    }
}

Modified the tgz decompression to support the tgz files of actual size more than 2GB

Thx for the update.
But it still did not help me, because it doesnt support single files bigger than 2GB.
the line
var buf = new byte[size];
throws an OverflowException when called with bigger values.

single byte array max size is that
https://stackoverflow.com/questions/3944320/maximum-length-of-byte/53967254