Many people seem to think, incorrectly, that the classes in the System.IO.Compression namespace, like GZipStream or DeflateStream, can create or read zip files. Not true. The System.IO.Compression namespace, available starting with .NET v2.0 for the desktop Framework and v3.5 for the Compact Framework, includes base class libraries supporting compression within streams – both the Deflate and Gzip formats are supported. But these classes are not directly useful for creating compressed ZIP archives. GZIP is not ZIP. Deflate is not ZIP. The GZipStream in System.IO.Compression is able to read and write GZIP streams, but that is not the same as reading or writing a zip file. Also, these classes deliver poor compression in practice, especially with binary data, or previously-compressed data. The sample demonstrates how to compress files into a single .gz file for download in ASP.NET using System.IO.Packaging. However a better approach is to use dotnetzip library available in codeplex http://dotnetzip.codeplex.com/ One cavet of using the ZipPackage to create Zips is that Packages contain a content type manifest named “[Content_Types].xml”.
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