We have a c# application that we were looking to migrate to the .net version of Xceed zip (for obvious reasons).  We have run into a problem where our clients cannot open the zip file generated.  The files open fine in WinZip 12, but the standard windows explorer zip support cannot extract files, nor can older versions of WinZip.

After a bit of investigation we found that the old XceedZip COM object (4.X) generated zip files that require a reader that can read Zip Specification version 2.0.  The real time zip component requires a reader that can read Zip specification version 4.5.  Is there any way to force either the real time zip component or the standard zip component to write the older file format?  If not we will probably have to continue using the COM xceed component or look for another solution.

Thanks

Joseph Johns
VirPack
jjohns@virpack.com

It all depends on the compression algorithm you are using.  For example, Deflated64 will require version 4.5.  But Deflated will work with 2.0.

As for Windows explorer, you would need to verify with Microsoft to know which format it supports, an which it does not, but "regular" formats should work.

Which version of Windows did you test it on, and which compression algorithm did you use?

Switching from the default of deflate64 to deflate made it able to open in windows explorer.  Thanks.

However, it does not fix the root issues.  The files produced are still zip spec version 4.5.  To put it shortly I need to produce a file that WinZip 8.1 could open.  It won't actually be opened by WinZip 8.1, but the clients have found that if that will open the file then their internal processes can open it.  WinZip 8.1 will not open the files produced by the real time zip as the header version is more advanced than it can read (it complains that the header is 56 bytes too long).  So can you force it to use the older file format, or will it always produce 4.5 files?

Thanks

It will always produce 4.5 version files.