When using wpf to develop, because of the log function, the log log4netd.dll class library is referenced.
After the class library is quoted, the report
Unknown build error "The assembly cannot be parsed because it is not preloaded" log4net, Version=1.2.9.0.
Later, I found out that related
Unknown build error. "Because there is no preload, the assembly's add-on cannot be resolved"
Basically, it is the problem of the old and new versions of the IDE. Just add the corresponding reference. For example, the error in this article is resolved after quoting the class library of log4net.dll.