Wpf itemssource binding not updating
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.The Update Source Trigger property of a binding controls how and when a changed value is sent back to the source.If we don't open the drop down first (skip steps 2 and 4), then all items will appear correctly in the drop down.Yeah, you need to open it to check the items, so after that all new items will not be added immediately.Default is, obviously, the default value of the Update Source Trigger.The other options are Property Changed, Lost Focus and Explicit.Just make sure that you don't update the source value more often than you actually need to.If you want the full control, you can use the Explicit value and then do the updates manually, but this does take a bit of the fun out of working with data bindings.
For that reason, I have added a button next to the Text Box, which will update the source value on demand.
However, since WPF is pretty good at controlling this for you, the default value should suffice for most cases, where you will get the best mix of a constantly updated UI and good performance.
For those situations where you need more control of the process, this property will definitely help though.
Instead of binding Items, you can use the interface, although the type of collection used does determine the way in which the control is updated when items are added to or removed.
When Items Source is set, the Items property cannot be used to control the displayed values.