GZipStream compression not working

c#, gzipstream

Solution

MSDN says: `The write operation might not occur immediately but is buffered until the buffer size is reached or until the Flush or Close method is called.`

In other words, the fact that all the Write operations are done doesn't mean the data is already in the `MemoryStream`. You have to do `gzipStream.Flush()` or close the gzipStream first.

Example:

using (var outStream = new MemoryStream())
{
    using (var fileStream = new FileStream(filename, FileMode.Open, FileAccess.Read))
    {
        using (var gzipStream = new GZipStream(outStream, CompressionMode.Compress))
        {
            fileStream.CopyTo(gzipStream);
        }

        Debug.WriteLine(
                "Compressed from {0} to {1} bytes", 
                fileStream.Length, 
                outStream.Length);

        // "outStream" is utilised here (persisted to a NoSql database).
    }
}

Also, ideally, put it outside of the FileStream as well - you want to close files as soon as you can, rather than waiting for some other processing to finish.

Problem

I'm trying to read in a file and compress it using GZipStream, like this: ``` using (var outStream = new MemoryStream()) { using (var fileStream = new FileStream(filename, FileMode.Open, FileAccess.Read)) { using (var gzipStream = new GZipStream(outStream, CompressionMode.Compress)) { fileStream.CopyTo(gzipStream); Debug.WriteLine( "Compressed from {0} to {1} bytes", fileStream.Length, outStream.Length); // "outStream" is utilised here (persisted to a NoSql database). } } } ``` The problem is that `outStream.Length` always shows 10 bytes. What am I doing wrong? I've tried calling `gzipStream.Close()` after the `fileStream.CopyTo` line (as suggested in other forums) but this seems to close `outStream` too, so the subsequent code that uses it falls over.

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