Andrzej.Kniola September 12, 2016 16:15
Hello,
@Eduardo - it isn’t a UiPath issue. The classes needed are in System.IO.Compression.FileSystem.dll (not imported by default, not only in UiPath but VS also). You will need to add a package with reference to it, which might be overkill - Cosmin’s way is much simpler.
If you want to use the .Net classes, there is a trick by the way… Only do this if you know what you’re doing, you might break your file if you mess up the structure 
If you open the .xaml in any text editor (Notepad++ is great for that), find assembly reference lines and the one you need, it will load it there.
So for example find this line:
UiPath.Excel
And just after it add (note it’s case sensitive!)
System.IO.Compression.FileSystem
It will then load the assembly you need to use the ZipFile class (and ZipFile extensions are there too, they’re pretty useful).
Using it that way you may load any assembly that is located in you most-up-to-date Reference Assemblies folder (by default: C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework.NETFramework[your_version])
Regards,
Andrzej