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 in my project namespace, and I tried Choose Item in rightclick menu, but I didn't find a way to add it.
As far as I know you can drag&drop your usercontrol in your current project to the toolbox. The problem is when you choose a different project the user control is gone. So I think you have to build a separate control library project:
In your solution, add a new project, however as a project template choose "Class Library". In THAT project, add a user control, and do everything you need to do. Once that's done, build it, and you'll have yourself a dll file (it can easily be found in the projects bin/debug folder.)
You can add this dll to your toolbox (right click add...) and it will stay there in all projects!
Right-click on toolbar then click on "choose item" in context menu. A dialog with registrated components pops up. in this dialog click "Browse" to select your assembly with the usercontrol you want to use.
PS. This assembly should be registrated before.