If you set the SelectedIndex after an item is added in the Items or ItemsSource of RadListBox, the selection doesn't work.
To work this around, use the SelectedItem property instead of SelectedIndex.
Available in LIB version 2018.1.205, it will be also available in the R1 2018 SP2 Release.
The issue can be reproduced in a scenario in which there are a RadListBox and a RadGridView defined and their SelectedItem properties are bound to the same property in the view model. The source collection of RadListBox contains some objects present in the one bound to RadGridView's ItemsSource. If the user selects an item in RadGridView that is also present in the items of RadListBox, the selection is performed in both controls as expected. However, when already having a selected item in both controls, if the user selects an item in RadGridView that is not present in the items of RadListBox, the selection in RadListBox is not cleared. Thus, in order to selected the previously selected item, it needs to be deselected and selected again. UPDATE: After the researching the issue, it seems that the logic for handling the case when a SelectedItem that is not present in the source collection is being set is slightly different for Silverlight and WPF. For the WPF version of the control a DependencyProperty.UnsetValue is used, whereas a null value is set for the Silverlight RadListBox. Thus, in Silverlight the selection is cleared and in WPF it is not. I am afraid, that we cannot commit ourselves to modifying this by-design implementation, as this will result in a braking change. With this in mind, I will update the status of the logged bug to Declined. What we can suggest as a workaround, would be to define a second calculated property in the view model and bind the SelectedItem of RadListBox to it. The logic in the property setter would be to set a null value if the SelectedItem is not present in the source collection of RadListBox.
A workaround is to use the SelectedItem of the control and get the value of the needed property of the item.
As a workaround, the ScrollingSettingsBehavior.ScrollStep attached property of the RadListBox control can be set to a value equal to that of the Height of the RadListBoxItems. Available in R3 2017 Official Release Version.
Can be reproduced when RadListBox is placed inside a Grid, a StackPanel with horizontal orientation or a WrapPanel. Available in LIB version 2016.1.125, it will be also available in the 2016 Q1 SP1.
Available in the 2016 Q1 Release.
The "auto scroll into the view on selection" functionality does not to work as expected if the ItemsPanel is changed and a selection was previously done.
Available in LIB version 2016.1.321, it will be also available in the 2016 Q2 Release.
Available in R3 2017 Official Release Version.