When controls update a property that is also the direct source of other bindings, the user interface can update automatically.We saw this with a Slider and a Text Block that were bound to the same value.In the previous article we saw how changes in a Text Box was not immediately sent back to the source.Instead, the source was updated only after focus was lost on the Text Box.The third and last Text Box uses the Property Changed value, which means that the source value will be updated each time the bound property changes, which it does in this case as soon as the text changes.Try running the example on your own machine and see how the three textboxes act completely different: The first value doesn't update before you click the button, the second value isn't updated until you leave the Text Box, while the third value updates automatically on each keystroke, text change etc.
Just make sure that you don't update the source value more often than you actually need to.
For example, if a read-only property is calculated according to other, data-bound properties, controls that are linked to the calculated value will not normally update.
If the source object is updated programmatically, these changes will not normally be reported to the user interface, which will continue to show old values.
This behavior is controlled by a property on the binding called Update Source Trigger.
It defaults to the value "Default", which basically means that the source is updated based on the property that you bind to.
Modify the constructor for the window, as follows: You can now run the program to see the results.