Wpf selecteditem not updating
My specific case was a bit more complex because I was binding to the page View Model (which I didn’t want to instantiate more than once as it made web service calls) to a Combo Box in a Data Template for a cell in a Grid View.
There wasn’t much documentation regarding that which I found that was helpful, so I’ll do another post about that later.
For the Selected Item and Selected Value bindings, I do not set a mode – this is because “Mode=Two Way” is the default.
Two Way means that we want to update the property on the View Model when the selection changes, and if the property on the View Model changes we want to update the Selected Item/Selected Value on the Combo Box. I've been intrigued by computers since I was 12, staying in at recess to code QBASIC on the old Apple II. NET Access Denied Active MQ Active MQ-Camel Attribute Behavior C# Camel Cassandra Combo Box Connecting Cross-Field Data Binding Data Context Display Member Path Double Click Enumerate Event Example Framework Element GAC IData Error Info INotify Property Changed Instances Items Source Karaf Lucandra Lucandra.
In our application we have a combo box that switches between different modes. So, if there are unsaved changes and the user selects new mode in the combo box, we want to Reverting using selection on step 1 makes sense, because the application did not officialy switch modes until the user said "yes", and we want the combo box to correctly reflect current mode. If we use MVVM, we have three entities related to the combo box selection: In an ideal world all three should be synchronized at all times, with possible exception of very brief transition states. NET 3.5, otherwise an MVVM application would never be able to set the selection programmatically.
Unfortunately, it turns out that if one uses MVVM and data binding, reverting user seletion in a combo box is difficult in . Unfortunately, the synchronization is broken in different ways in . Roughly, the combo box turns "deaf" to view model updates for the duration of "selection changed" windows message, probably to prevent infinite loops.
Very simple scenario : I have a user control which features a listbox, a textblock which reflects the selected item, and a button which should be enabled if there is a selection. The problem is that when I select an item from the list, the Has Selection property changes to true, it fires the Property Changed event as defined by INotify Property Changed (I have stepped through the code to verify this) but the button steadfastly refuses to enable.
Once the selection message processing is finished, the combo box is willing to listen to updates again.Now that we’ve got a decent understanding of the common binding properties of a Selector control (I hope! Given the following classes (only class signatures; the full sample project including source code is attached to this post): Note the use of “Mode=One Way” in my Items Source bindings.This indicates to the binding that we’re only going to be updating the binding target (the Combo Box’s Items collection in this case).NET version and what is done in the property setter.I used to it to research the issue and understand how the internals work.