.NET Windows Forms in a Nutshell

Custom Type Editors

The PropertyGrid allows us to replace the built-in text-based editing. We can assign a custom editor that supplies its own user interface. The framework calls such editors UI Type Editors. Not only can these provide a special-purpose editing user interface, they can change how the property’s value is displayed even when we are not editing its value.

Supplying a UI Type Editor is simple. We simply write a class that derives from System.Drawing.Design.UITypeEditor and associate it with the property or type in question using the Editor attribute. We only need to override two methods in our editor class. The first, GetEditStyle, is called to determine what style of editing UI we support; we can open a standalone modal dialog, drop down a UI in the PropertyGrid itself, or supply no editing UI. The second method, EditValue, is called when we are required to show our editing interface.

Let us add a new property to our CustomerDetails class (as shown in Example 8-22) so that we can supply a custom editing user interface for it. The new property is Happiness, and it indicates the level of customer satisfaction, on a range of 0 to 100%. It is shown in Examples Example 8-23 and Example 8-24. The editor has been specified with the Editor attribute. (The second parameter is always required to be UITypeEditor in the current version of the framework.) The property’s type here is int or Integer, but we can provide custom UI editors for any type, whether it is a custom ...