Visual Basic 2005: A Developer's Notebook

Compress and Decompress Data

Even with the ever-increasing capacity of hard drives and the falling price of computer memory, it still pays to save space. In .NET 2.0, a new System.IO.Compression namespace makes it easy for a VB 2005 programmer to compress data as she writes it to a stream, and decompress data as she reads it from a stream.

Note

Need to save space before you store data in a file or database? . NET 2.0 makes compression and decompression easy.

How do I do that?

The new System.IO.Compression namespace introduces two new stream classes: GZipStream and DeflateStream, which, as you'd guess, are used to compress and decompress streams of data.

The algorithms used by these classes are lossless, which means that when you compress and decompress your data, you won't lose any information.

To use compression, you need to understand that a compression stream wraps another stream. For example, if you want to write some compressed data to a file, you first create a FileStream for the file. Then, you wrap the FileStream with the GZipStream or DeflateStream. Here's how it works:

Dim fsWrite As New FileStream(FileName, FileMode.Create)
Dim CompressStream As New GZipStream(fsWrite, CompressionMode.Compress)

Now, if you want to write data to the file, you use the GZipStream. The GZipStream compresses that data, and then writes the compressed data to the wrapped FileStream, which then writes it to the underlying file. If you skip this process and write directly to the FileStream, you'll ...