If I understand your question correctly, you have two classes Softwares.SoftwareXSDin different assemblies (main application and library), whose full name is identical.
To solve this problem, go to Solution Explorer in Visual Studio, expand Links, right-click the link to your library, and select properties.
In “Aliases,” replace “global” with another nickname, for example. "Library".
Now you can fix the errors as follows:
global::Softwares.SoftwareXSD
library::Softwares.SoftwareXSD
However, I still recommend that you choose unique names for your classes.