I made a usercontrol in my project, and after building project, I need to put it in my toolbox, and use it as a common control. but i can\'t. the UserControl
is
There are a couple of ways.
In your original Project, choose File|Export template
Then select ItemTemplate and follow the wizard.
Move your UserControl to a separate ClassLibrary (and fix namespaces etc).
Add a ref to the classlibrary from Projects that need it. Don't bother with the GAC or anything, just the DLL file.
I would not advice putting a UserControl in the normal ToolBox, but it can be done. See the answer from @Arseny