If you need a custom editor to edit a specific data, you can use one of the following approaches:

1. Use CellEditTemplate property of the GridViewColumn.
2. Create a custom column by inheriting from GridViewBoundColumnBase.

As almost anything in our life both approaches have some advantages and disadvantages. Although it is quite easy to implement the first option, there are some significant disadvantages like not so usable with many RadGridView instances, and more important this bypasses the RadGridView validation and editing engine. For more information about this approach you can take a look at this online example....

With the next Q3 2009 official release we are introducing a significant improvement to the validation mechanism of the RadGridView control. If we compare the new validation to the previous versions we add another validation layer (Data Layer) and refactoring of the related events. In a series of blog posts I’ll try to clarify this mechanism with several small examples. I’ll start the series with validation for a single cell.

How to: Validate data on a cell (property) level with RadGridView for Silverlight and WPF

The cell validation occurs when a GridViewCell is edited and its new data ...