I have added this control to one pop-up.
After opening the pop-up list of elements is displayed in this control.
For the first time changing the selected item, I need to select it twice. The selected value is not getting changed on the first click.
from 2nd time onwards it is working correctly.
Also if we focus out and again focus, then selection will not work again same as the first time.
This way I have added a control.
<sf3:SfMultiColumnDropDownControl Width="125" TabIndex="6" Margin="10,0,0,0" ItemsSource="{Binding ClientConnectionNoList}" SelectionMode="Single" SelectedItem="{Binding SelClientConnectionNo, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" DisplayMember="ConnectionNo" ValueMember="ConnectionNo" IsEnabled="{Binding IsChangeValueEnabled,UpdateSourceTrigger=PropertyChanged}" GridColumnSizer="Auto" PopupHeight="200" PopupWidth="200"></sf3:SfMultiColumnDropDownControl>