I am wrapping up a WinForm project that required me to create some custom user controls. While Visual Studio makes that stupid easy, there are things that can trip you up. Mainly by making things not being available when you import them into the project. Your WinForm user control is missing so here is what to do.
Causes of a Missing WinForm User Control
The number one cause for me having this issue is that I have a different version of .NET for each project. The solution is pretty simple. First open up the properties for each project by right clicking on the project in the Solution Explorer and selecting Properties in the context menu. You want to make sure that your Target Framework is the same. When you get the right. Save that application and do a new build. Things should just start working.
If that doesn’t work then it may be tied to being a referenced control. If that happens to you, open the form you want to add the controller so you get the Toolbox section. Right click and select the Choose Items… option in the context menu. In that section you want to press the browse button.
Find your dll or exe and press ok. You may need to make sure the user controls are checked or they will still be missing.
There are other more fringe things that could cause this. I have not personally run into them but if neither of those solution fix your problem try going to Tools->Option->Winform Designer-> General->AutoToolboxPopulate. Set that to true.
Next on the list of things to try is make sure your control is public. Otherwise the external class cannot access it.
Finally, try to clean and then build the project and do a rebuild or take a real flyer and reset the toolbox.
These last items have never solved my user control issues but they are commonly referenced things to try. I suspect that was from versions past but if you are playing in Visual Studio 2010 still, it might be worth a try to solve when your WinForm user control is missing.
As usual leave any comments down below.