I was having this same issue. I am working in Visual Studio 2010.
My user control library is written in C# and my project I'am importing it into is in Visual Basic.
If I had the C# project in my solution, the custom user controls would show up automatically. But if I only referenced the DLL it would not load the custom user controls from the referenced library into the "Toolbox".
The above post that mentions finding the file in explorer and dragging and dropping it into the toolbox solved the problem. This is a very strange way of behaving. VB user control libraries don't require this step.
This has been an issue I have had sitting on the burner for the last 2 years.
I would up-vote the previous answer but I don't have enough rep yet.
This post could use some better tags, cause it was buried on most of my google searches.
So
- Reference the user control library
- Drop the DLL file into the tool box.
One question I have in regards to this is: what happens if you change the project reference to the DLL (because it moved) and not attempt to update the toolbox reference (by removing the control from the toolbox and dragging and dropping the DLL from the new location)?
F5
of some sort probably is better but they didn't give an option... – Epineurium