asp.net 4.0 - When I create a custom control that inherits from HtmlContainerControl, I can't get it to show up in the VS Toolbox -

I have tried two ways to add custom controls to the toolbox.

First of all, I tried to drag DLL to my toolbox, but only a few controls appeared.

Then, when I did "select item", then only some controls were seen.

The Web UI. Html control None of my custom controls are available from the HTML Container control.

However, if I control those sections of the Web

Thanks

P> Do you decorate it with attributes?