The problem is that I have three usercontrols for three shapes, two of them are displayed, and one is not (circled in red, three textboxes should be visible in the control). It is not displayed neither in the form designer, nor during the program execution. I tried everything, exclude from the project, re-add, rebuild, clean, delete the control completely and throw it on a new one. I do not know what to do anymore, I rummaged through almost everything, even the English-speaking forums. In the code it is described exactly the same as the other two, which are displayed.
Thanks for the answer!
