Programming WPF, 2nd Edition

Where Are We?

Data binding is about keeping two values synchronized. One value, the target, is a dependency property, typically on a UI element. The other, the source, is a CLR property—the result of an XPath expression, a dependency property, or a dynamic property used by objects like those provided by ADO.NET that don't know what the data is going to be until runtime. By default, as either the target or the source changes, the other value is updated, but you can control that with the alternate binding modes (e.g., one-way, one-time, etc.). As data changes, type conversion happens automatically if a converter is available, although you can take full control of the conversion and validation process if you so choose, doing things like restricting data ranges and converting data formats, or even automatically showing errors in tool tips. You might think that WPF data binding is powerful with these features, and you'd be right, but we've just touched on the bare essentials associated with bindings to properties on a single object. When you've got a list of objects as your data source, you've got all kinds of other facilities, which is the subject of the next chapter.