I'm wondering if the same applies to .NET as well? E.g. I want to create some custom controls, such as GridView. Can I just add a class into my App_Code folder or I have to create a separate new project?

>>>Do I understand correctly that a good practice is to create a separate solution for my class library? And this solution/project would have to be references in all my other solutions where the classes will be used, right?
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>>Well, it depends. We have our framework projects in every application solution (controlled by source control, TFS in our case ... VSS would work too). That way, references to them are project references rather than DLL references, plus it's easier to look at base class code if you want/need to, since it's all in your app's solution. However, you *can* have your framework projects in a separate solution if you wish and use DLL references to them in your app's solution. We just thought the first methodology was easier for the newbies in our company.
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>I like the way you decided to have your framework projects in every application solution. But how do you do it, specifically? When you start a new application, do you copy your framework projects into the folder for the new application solution? I am very sorry for not getting something that is probably very obvious to you. Thank you.
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>Here is an example:
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>Say I will have my framework in a folder:
>D:\VS2005\MYFRAMEWORK
>Then I will have all my VS project in folders:
>D:\VS2005\Apps\Appl1\
>D:\VS2005\Apps\Appl2\
>and so on.
>
>So I will have to copy all code from D:\VS2005\MYFRAMEWORK in each one of the application solutions (D:\VS2005\Apps\Appl1|2)?
>
>Again, thank you.