RadCombobox.SelectedItemText returns null

[greeshmakr]

Telerik.Windows.Controls.RadCombobox.SelectedItemText returns null after screen reloads. I am able to read the Selected Item by using Visual UIA Verify. But, was unable to read it through automation code using TestStack.White framework. Below is the RadComboBox details from xaml page

<telerik:RadComboBox x:Name="ComboBox1"
Style="{StaticResource styleRadComboBoxTransparent}"
ItemsSource="{Binding FitAlgorithms}"
SelectedItem="{Binding SelectedBeadPlex.CurveFitData.FitAlgorithm, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
IsEnabled="{Binding EditEnabled}"
Margin="0,5,0,0"
>
telerik:RadComboBox.ItemTemplate



</telerik:RadComboBox.ItemTemplate>

But,
ComboBox1.SelectedItemText returns null in the Automation code. Please share your suggestions.

Thanks.