If you wish to use the DeflateStream to compress data while reading, you can create a DeflateStream with CompressionMode.Compress, providing an uncompressed data stream. Then call Read() on that DeflateStream, and the data read will be compressed as you read. If you wish to use the DeflateStream to decompress data while reading, you can create a DeflateStream with CompressionMode.Decompress, providing a readable compressed data stream. Then call Read() on that DeflateStream, and the data read will be decompressed as you read.
A DeflateStream can be used for Read() or Write(), but not both.