Cannot find `ZipArchive` in the “System.IO.Compression” namespace
问题 My question is related to I didn't find "ZipFile" class in the "System.IO.Compression" namespace But I have referenced the DLL's for my 4.5.1 webforms project: Properties of my project give me: Target framework: .Net Framework 4.5.1. and the web.config: <compilation debug="true" targetFramework="4.5" /> What am I missing? The solution was to manually reference the assemblies in the web.config But why? Why wasn't the checkbox in the add reference dialog insufficient? <assemblies> <add assembly