how to add a user control from a dll(already referenced) to ui in design mode?

If i first add it to the toolbox, an exception will be thrown, saying the dll is already referenced.

and i hate to add it to ui programmatically.

any idea? i have to add it programmatically?

how about removing previous reference and browsing to the dll ?

firs add a new user control to your project after coding has finished, then Build your project. so you'll see the your created control appears in the toolbox(at the top), then just drag & drop it on your form or any ui and if you want to load a control from a DLL just add a new tab in your tool box then right click on it and select "choose items..." and then in the .Net Framework Components tab click "browse" and navigate to your dll , and then open the dll file and confirm the choose items dialog and you see the user control is now ready for drag & drop in your tool box :)