>Anyone using targetFramework attribute of the compilation tag in web.config?
>
>I am interested to know what are your reasons for using it.
>
>If the .NET Framework installed on the server is 4.5.1 and that attribute is set to 4.0, is it correct to say that .NET Framework 4.5.1 will not be fully used and the application is forced to run in 4.0? Which means, if I need to use an attribute that is only supported in 4.5.1, having that attribute set like that, would it make the attribute useless in that case?

Yes. If you target, say, 4.0 then any attempt to use newer functionality in 4.5.1 will not be available. In most cases that mean that the app won't compile. In a few obscure cases you may just get different behaviour from that which was expected.

BTW, the settings in web.config are automatically updated if you change the 'Target Framework' in the 'Project Properties' page...