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Asked: 2026-05-11T03:30:27+00:00

I used the code below to compress files and they keep growing instead of

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I used the code below to compress files and they keep growing instead of shrinking. I comressed a 4 kb file and it became 6. That is understandable for a small file because of the compression overhead. I tried a 400 mb file and it became 628 mb after compressing. What is wrong? See the code. (.net 2.0)

Public Sub Compress(ByVal infile As String, ByVal outfile As String)     Dim sourceFile As FileStream = File.OpenRead(inFile)     Dim destFile As FileStream = File.Create(outfile)      Dim compStream As New GZipStream(destFile, CompressionMode.Compress)      Dim myByte As Integer = sourceFile.ReadByte()     While myByte <> -1         compStream.WriteByte(CType(myByte, Byte))         myByte = sourceFile.ReadByte()     End While      sourceFile.Close()     destFile.Close() End Sub
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  1. Are you sure that writing byte by byte to the stream is a really good idea? It will certainly not have ideal performance characteristics and maybe that’s what confuses the gzip compressing algorithm too.

    Also, it might happen that the data you are trying to compress is just not really well-compressable. If I were you I would try your code with a text document of the same size as text documents tend to compress much better than random binary.

    Also, you could try using a pure DeflateStream as opposed to a GZipStream as they both use the same compression algorithm (deflate), the only difference is that gzip adds some additional data (like error checking) so a DeflateStream might yield smaller results.

    My VB.NET is a bit rusty so I’ll rather not try to write a code example in VB.NET. Instead, here’s how you should do it in C#, it should be relatively straightforward to translate it to VB.NET for someone with a bit of experience: (or maybe someone who is good at VB.NET could edit my post and translate it to VB.NET)

    FileStream sourceFile; GZipStream compStream;  byte[] buffer = new byte[65536]; int bytesRead = 0; while (bytesRead = sourceFile.Read(buffer, 0, 65536) > 0) {      compStream.Write(buffer, 0, bytesRead); }
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