How to: Display a Control in the Choose Toolbox Items Dialog Box
As you develop and distribute controls, you may want those controls to appear in the Choose Toolbox Items dialog box, which is displayed when you right-click the Toolbox and select Choose Items. You can enable your control to appear in this dialog box by using the AssemblyFoldersEx registration procedure.
To display your control in the Choose Toolbox Items dialog box
Install your control assembly to the global assembly cache. For more information, see How to: Install an Assembly into the Global Assembly Cache
Register your control and its associated design-time assemblies by using the AssemblyFoldersEx registration procedure. AssemblyFoldersEx is a registry location where third-party vendors store paths for each version of the framework that they support. Design-time resolution can look in this registry location to find reference assemblies. The registry script can specify the controls you want to appear in the Toolbox. For more information, see Deploying a Custom Control and Design-time Assemblies (Visual Studio 2013).