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RadComboBox pushing null to SelectedItem/SelectedValue upon load

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ComboBox

This is a migrated thread and some comments may be shown as answers.

yonadav asked on 04 Feb 2010, 07:33 PM

Hi All,

This is another issue we've started encountering only after the move to Q3 SP2 2009 (we were at Q3 2009 yesterday).

If, for example, we've defined a RadComboBox like so:

                    <telerik:RadComboBox SelectedValue="{Binding Setting}"         
                                              ItemsSource="{Binding PossibleValues,Mode=OneWay}"         
                                              SelectedValuePath="UniqueName"         
                                              DisplayMemberPath="FriendlyName" />         

And we place a breakpoint in the Setting property's set function (noticed its bound to SelectedValue). Then every time the RadComboBox we get a call to set with a value of null. Similar things happen when binding to SelectedItem.

Oddly enough, we did not have this issue in Q3 2009 (re-tested today).

Any ideas?

Thanks,

yonadav

15 Answers, 1 is accepted

answered on 15 Mar 2010, 01:35 PM

Hi yonadav,

The problem comes from the fact that when RadComboBox.ItemsSource is changed (in this case with null) combo box changes its selected index (value) and through binding updates underlying data object (also with null). I think that this is an expected behavior of the RadComboBox.
In our case (RadGridView and CellEditTemplate) the grid control sets RadComboBox.DataContext to null when cell edit is ended which causes the problem.

We've already fixed the issue and fix will be available with the next latest internal build (every Friday).

Unfortunately the fix is within RadGridView domain. So I think that this won't fix your scenario with "MindScape WPF Property Grid".

Don't hesitate to contact us if you have other questions.

All the best,
Nedyalko Nikolov
the Telerik team

Do you want to have your say when we set our development plans? Do you want to know when a feature you care about is added or when a bug fixed? Explore the Telerik Public Issue Tracking system and vote to affect the priority of the items.

answered on 27 Jul 2011, 04:49 AM

We're experiencing the same problem with the latest controls (Version 2011.2.712.1040).
The RadComboBox's SelectedItem is bound to a property on the ViewModel.
However the property on load is being set to Null by the RadComboBox.

Our RadComboBox sits within a ControlTemplate....

<ControlTemplate x:Key="EditAppointmentTemplate"

TargetType="TelerikSchedule:SchedulerDialog">

...and the RadComboBox sits within a Grid.

When we replace the RadComboBox with a normal ComboBox control - the problem goes away.
Is there a fix for this - we really would like to keep using the Telerik RadComboBox.

Thanks

EDIT----Further to this...
If I open my EditAppointmentTemplate every alternate time it works. I do not select another appointment in between this.
So
Open 1st time - RadComboBox sets the property to nulll.
Open 2nd time - RadComboBox gets the property correctly - based on RIA value
Open 3rd time - - RadComboBox sets the property to nulll.
Open 4th time - - RadComboBox sets the property correctly - base on RIA value
etc etc

answered on 18 Oct 2012, 04:09 PM

I found a work around that may or may not apply to your situation. I ran into what looks like the same issue. I made sure my SelectedValuePath and DisplayValuePath are set correctly. The combo box is filled with the correct objects and values. But, If I try to do a two-way binding to the SelectedValue property, a null value is passed by the control and sets the value of the target object to null.

What I did was create a command that sets the value and passes a commandParameter to the command. I use the command to set the value of the desired property and use OneWay binding on the SelectedValue to display the selected object in the comboBox.

<telerik:RadComboBox x:Name="rcbLevel1" d:LayoutOverrides="Height" ItemsSource="{Binding InsertEditItem.Level1s, Mode=TwoWay}" SelectedValue="{Binding InsertEditItem.CurrentItem.Level1}"

SelectedValuePath="Description" EmptyText="Select a category..." IsEnabled="{Binding InsertEditItem.Level1IsEnabled, Mode=TwoWay}" Command="{Binding InsertEditItem.SetActiveLevel1Command, Mode=OneWay}" CommandParameter="{Binding SelectedItem, ElementName=rcbLevel1}" DisplayMemberPath="Description" IsEditable="True"/>