Feedback when loading data asynchronously

Question

I have a ComboBox whose ItemsSource is bound to an ObjectDataProvider that has its IsAsynchronous property set to true. Inside the method that loads the data , I put a Wait for 10 seconds, to simulate a long loading time for this data.

The Asynchronous loading works great - the entire window is still responsive, and after 10 seconds I see the ComboBox dropdown populated.

I would like to alert the user that this specific ComboBox is loading data, during that 10 second wait time. Something like a progressBar in the background of the control, that is enabled only while a certain 'isLoading' property or whatever is set to true. Is it possible to accomplish this?

Thanks.

punker76 · Accepted Answer · 2011-12-09 20:02:52Z

6

this looks like the Priority Binding could be a solution for you

<ListBox>
    <ListBox.ItemsSource>
    <PriorityBinding>
        <!-- highest priority sources are first in the list -->
        <Binding Path="LongLoadingCollection" IsAsync="True" />
        <!-- this contains only one item like "loading data..." -->
        <Binding Path="LoadMessage" IsAsync="True" />
    </PriorityBinding>
    </ListBox.ItemsSource>
</ListBox>

enter image description here

here is an good tutorial for Priority Bindings
http://www.switchonthecode.com/tutorials/wpf-tutorial-priority-bindings

or take a look at msdn
http://msdn.microsoft.com/en-us/library/system.windows.data.prioritybinding.aspx

hope this helps

edited Dec 9, 2011 at 20:02

answered Dec 9, 2011 at 19:29

punker76

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1 Comment

brunnerh Over a year ago

Please try to make your answer stand on its own, off-site links can be useful but they tend to die, if you link off-site see if the official documentation sufficient, it is to be preferred to some random blog, and if the official documentation is gone the technology it documented probably is too: PriorityBinding

Tim · Accepted Answer · 2011-12-09 19:12:09Z

0

It doesn't appear that the ObjectDataProvider has any properties to say when it is and isn't retrieving data.

It depends on your architecture, but you could expose properties that give a "load state" to your object that contains the method that loads the data. Then you could bind a progress bar or other "Please Wait..." kind of UI to that new state property.

answered Dec 9, 2011 at 19:12

Tim

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