GZipStream - do not write write all compressed data even with a flash?

Question

I have a nasty problem with gzipstream.Net 3.5 targeting. This is my first gzipstream experience, however I modeled after several tutorials, including here , and I'm still stuck.

My application serializes the datatable for xml and inserts it into the database, storing the compressed data in the varbinary (max) field, as well as the original length of the uncompressed buffer. Then, when I need it, I retrieve this data and unpack it and recreate the datatable. Decompression seems to fail.

EDIT: Unfortunately, after changing GetBuffer to ToArray, as suggested, my problem remains. Code updated below

Compression Code:

DataTable dt = new DataTable("MyUnit");
//do stuff with dt
//okay...  now compress the table
using (MemoryStream xmlstream = new MemoryStream())
{
    //instead of stream, use xmlwriter?
    System.Xml.XmlWriterSettings settings = new System.Xml.XmlWriterSettings();
    settings.Encoding = Encoding.GetEncoding(1252);
    settings.Indent = false;
    System.Xml.XmlWriter writer = System.Xml.XmlWriter.Create(xmlstream, settings);
    try
    {
        dt.WriteXml(writer);
        writer.Flush();
    }
    catch (ArgumentException)
    {
        //likely an encoding issue...  okay, base64 encode it
        var base64 = Convert.ToBase64String(xmlstream.ToArray());
        xmlstream.Write(Encoding.GetEncoding(1252).GetBytes(base64), 0, Encoding.GetEncoding(1252).GetBytes(base64).Length);
    }

    using (MemoryStream zipstream = new MemoryStream())
    {
        GZipStream zip = new GZipStream(zipstream, CompressionMode.Compress);
        log.DebugFormat("Compressing commands...");
        zip.Write(xmlstream.GetBuffer(), 0, xmlstream.ToArray().Length);
        zip.Flush();
        float ratio = (float)zipstream.ToArray().Length / (float)xmlstream.ToArray().Length;
        log.InfoFormat("Resulting compressed size is {0:P2} of original", ratio);

        using (SqlCommand cmd = new SqlCommand())
        {
            cmd.CommandText = "INSERT INTO tinydup (lastid, command, compressedlength) VALUES (@lastid,@compressed,@length)";
            cmd.Connection = db;
            cmd.Parameters.Add("@lastid", SqlDbType.Int).Value = lastid;
            cmd.Parameters.Add("@compressed", SqlDbType.VarBinary).Value = zipstream.ToArray();
            cmd.Parameters.Add("@length", SqlDbType.Int).Value = xmlstream.ToArray().Length;
            cmd.ExecuteNonQuery();

        }
    }

Decompression Code:

/* This is an encapsulation of what I get from the database
 public class DupUnit{
    public uint lastid;
    public uint complength;
    public byte[] compressed;
}*/
  //I have already retrieved my list of work to do from the database in a List<Dupunit> dupunits
foreach (DupUnit unit in dupunits)
{
    DataSet ds = new DataSet();
    //DataTable dt = new DataTable();
    //uncompress and extract to original datatable
    try
    {
        using (MemoryStream zipstream = new MemoryStream(unit.compressed))
        {
            GZipStream zip = new GZipStream(zipstream, CompressionMode.Decompress);
            byte[] xmlbits = new byte[unit.complength];
            //WHY ARE YOU ALWAYS 0!!!!!!!!
            int bytesdecompressed = zip.Read(xmlbits, 0, unit.compressed.Length);
            MemoryStream xmlstream = new MemoryStream(xmlbits);
            log.DebugFormat("Uncompressed XML against {0} is: {1}", m_source.DSN, Encoding.GetEncoding(1252).GetString(xmlstream.ToArray()));
            try{
               ds.ReadXml(xmlstream);
            }catch(Exception)
            {
                //it may have been base64 encoded...  decode first.
               ds.ReadXml(Encoding.GetEncoding(1254).GetString(
                 Convert.FromBase64String(
                 Encoding.GetEncoding(1254).GetString(xmlstream.ToArray())))
                 );
            }
            xmlstream.Dispose();
        }
    }
    catch (Exception e)
    {
        log.Error(e);
        Thread.Sleep(1000);//sleep a sec!
        continue;
    }

... bytesdecompressed 0. ? ?

2:

, . :

   GZipStream zip = new GZipStream(zipstream, CompressionMode.Decompress);
   byte[] xmlbits = new byte[unit.complength];
   int offset = 0;
   while (zip.CanRead && offset < xmlbits.Length)
   {
       while (zip.Read(xmlbits, offset, 1) == 0) ;
       offset++;
   }

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