I would like to do the following all in memory without writing to disk on the client's machine.

Zip an in-memory DataTable in .NET 2.0 (C#) to memory (not disk).  Then I'll send it ( string/byte/stream ..  whatever it's called) to our web service.

 I found some code to change the DataTable into a stream, so I think that's the first part. thanks!

 You can use a MemoryStream or a StringWriter with these overloads to keep it all in memory.

string result;
using (StringWriter sw = new StringWriter()) {
   dataTable.WriteXml(sw);
   result = sw.ToString();
}

If you don't actually need a string but read-only, process able XML, it's a better idea to use MemoryStream and XPathDocument:

XPathDocument result;
using (MemoryStream ms = new MemoryStream()) {
   dataTable.WriteXml(ms);
   ms.Position = 0;
   result = new XPathDocument(ms);
}

You can use a MemoryFile to write the table to it, and use it to copy it to a zip archive in memory, and then use this archive to send it to the Web Service, via a stream for example.

 e.g.:

     AbstractFile dest = new MemoryFile( "ram", "DataTable" );

     using( Stream destStream = dest.OpenWrite( true ) )

       string line = "Try with this text";

       System.Text.Encoding.ASCII.GetBytes( line );

       byte[] buffer = System.Text.Encoding.ASCII.GetBytes( line );

     AbstractFile memZip = new MemoryFile( "Ram", "archive.zip" );

     ZipArchive archive = new ZipArchive( memZip );

     dest.CopyTo( archive, true );

     ZippedFile zippedFile = new ZippedFile( memZip, "DataTable" );

     AbstractFile unzippedFile = new MemoryFile();

     zippedFile.CopyTo( unzippedFile, true );

     using( Stream stream = unzippedFile.OpenRead() )

       byte[] buffer = new byte[ stream.Length ];

       Console.WriteLine( System.Text.Encoding.ASCII.GetString( buffer ) );