Chapter 8: Design-Time Support for Custom Controls

Overview

The Custom Controls you have explored so far are full of promise. Being able to drop a tool like a directory browser or thumbnail viewer directly into your application without writing a single line of extra code is a remarkable advantage. However, there is one caveat. Though your custom controls perform wonders at runtime, many of them act oddly while a form is being designed. By default, only user controls appear in the toolbox, and even they only appear with a generic icon. Inherited controls need to be created in code, unless you create a similar control and manually edit the hidden designer instructions. Even if you use this trick, the results aren't always what you expect.

This chapter sorts through these quirks and shows how to create a control that behaves properly at design time. Some of the topics this chapter tackles include:

Using attributes to classify and describe properties and other aspects of your control.

Adding your control to the toolbox—with an icon.

Using prebuilt UITypeEditor classes that allow directory names, collections, and other property types to be edited at design time.

Creating your own UITypeEditor classes that allow your control to be configured with custom dialog windows.

Using control designers to filter out unused properties, add designer wizards, and other tricks.

Licensing your controls.

This chapter will explore these topics, and use them to revise some of the examples introduced in the previous chapter.