how to create a class library file and how to implement in web forms?
2 Answers
Just right-click the solution in Solution Explorer and choose Add->New Project. As the project type, choose "Class Library".
As to how to use it, it's easy if you used a Web Application Project (File->New Project), but I don't know how to do it if you used File->New Web Site (I never use that).
If you used a Web Application Project, then just right-click the project and choose "Add Reference". Then click the "Project" tab, and select the class library project from the list. Click ok and you're done.