//using System.IO;
//using System.IO.Compression;

/// <summary>
/// GZipStream压缩字符串
/// </summary>
/// <param name="str"></param>
/// <returns></returns>
static Stream GZipCompress(string str)
{
    MemoryStream msReturn;
    using (MemoryStream msTemp = new MemoryStream())
    {
        using (GZipStream gz = new GZipStream(msTemp, CompressionMode.Compress, true))
        {
            using (BinaryWriter writer = new BinaryWriter(gz))
            {
                writer.Write(Encoding.UTF8.GetBytes(str));
            }
            gz.Close();
            msReturn = new MemoryStream(msTemp.GetBuffer(), 0, (int)msTemp.Length);
        }
    }
    return msReturn;
}

/// <summary>
/// GZipStream解压字符串
/// </summary>
/// <param name="stream"></param>
/// <returns></returns>
static string GZipDecompress(Stream stream)
{
    using (GZipStream gz = new GZipStream(stream, CompressionMode.Decompress))
    {
        using (StreamReader reader = new StreamReader(gz, Encoding.UTF8))
        {
            return reader.ReadToEnd();
        }
    }
}

static Stream GZipCompress(string str)
{
    MemoryStream msReturn = new MemoryStream();

    using (MemoryStream msTemp = new MemoryStream())
    {
        using (GZipStream gz = new GZipStream(msTemp, CompressionMode.Compress, true))
        {
            using (BinaryWriter writer = new BinaryWriter(gz))
            {
                writer.Write(Encoding.UTF8.GetBytes(str));
            }

            gz.Close();
            msReturn.Write(msTemp.GetBuffer(), 0, (int)msTemp.Length);
            msReturn.Seek(0, SeekOrigin.Begin);//非常重要
        }
    }

    return msReturn;
}