C#- MD5 Hash

  using System.Security.Cryptography;

    public string HashFile(string filePath)
    {
        using (FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read))
        {
            return HashFile(fs);
        }
    }

    public string HashFile( FileStream stream )
    {
        StringBuilder sb = new StringBuilder();

        if( stream != null )
        {
            stream.Seek( 0, SeekOrigin.Begin );

            MD5 md5 = MD5CryptoServiceProvider.Create();
            byte[] hash = md5.ComputeHash( stream );
            foreach( byte b in hash )
                sb.Append( b.ToString( "x2" ) );

            stream.Seek( 0, SeekOrigin.Begin );
        }

        return sb.ToString();
    }
http://stackoverflow.com/questions/2150455/how-do-i-create-an-md5-hash-digest-from-a-text-file