Is it possible to combine .Net GZip compression and SQL Server compression? - .net-core

Question

For various reasons related to network bandwidth and performance we have an application with large Unicode strings converted to byte arrays compressed with the GZipStream .Net framework (.Net core 3.1) functionality.
We want to store these in a SQL Server 2017 varbinary(max) column for later retrieval and decompression - this works fine using the same GZipStream library to decompress.
We would also like to take advantage of the T-SQL Decompress function to be able to query the data on the DB server (without having to bring it all back into .Net and decompress it there)
Whilst Decompress does seem to work (as in it doesn't throw an error and it produces a binary output that can be cast to nvarchar(max)), the resulting nvarchar is totally different from the original source - it actually crashes SSMS when displayed!
This is not a problem if we pass the decompressed string into SQL Server and compress it there using the Compress function, but we do not want to do this because it requires additional decompress step and extra bandwidth consumption.
I have ensured we're on CU20 of SQL Server 2017, so I don't think it's a patching problem.
I have tried the using the different compression ratio options in the .Net library but they all produce the same problem.
It would appear that despite both being GZip compression that the T-SQL and .Net compression algorithms are not compatible, but if anyone has succeeded in combining the two, I would appreciate hearing how.

Answer 1

Arrgh... I was being an idiot! My source strings (they were XML) were in UTF-8 so this worked:
using (var compressStream = new MemoryStream())
using (var compressor = new GZipStream(compressStream, CompressionMode.Compress))
{
compressor.Write(Encoding.UTF8.GetBytes(largeString));
compressor.Close();
var bytesToWriteToSQLVarbinaryMax = compressStream.ToArray();
}
And then I could do:
SELECT Cast(Decompress(bytes) AS varchar(max)) FROM compressedTable