How to group items in suggestion box in Xamarin.Forms Autocomplete control

<ContentPage.Content>
        <StackLayout Padding="20">
            <autoComplete:SfAutoComplete x:Name="autoComplete" Grid.Row="0" DataSource="{Binding contactsinfo}" DisplayMemberPath="ContactName" DropDownHeaderViewHeight="100" DropDownItemHeight="0" FilteredItems="{Binding FilteredCollection, Mode=TwoWay}" HeightRequest="40" NoResultsFoundTextColor="Gray" SelectedItem="{Binding SelectionObject}" SuggestionBoxPlacement="Bottom">
                <autoComplete:SfAutoComplete.DropDownHeaderView>
                    <syncfusion:SfListView x:Name="listView" BackgroundColor="AliceBlue" HeightRequest="800" ItemSpacing="1" ItemTapped="listView_ItemTapped" ItemsSource="{Binding FilteredCollection}" SelectedItem="{Binding SelectionObject}" SelectionMode="Single">
                        <syncfusion:SfListView.ItemTemplate>
                            <DataTemplate>
                                <Grid x:Name="grid" RowSpacing="0">
                                    <Grid.RowDefinitions>
                                        <RowDefinition Height="*" />
                                        <RowDefinition Height="1" />
                                    </Grid.RowDefinitions>
                                    <Grid RowSpacing="0">
                                        <Grid.ColumnDefinitions>
                                            <ColumnDefinition Width="70" />
                                            <ColumnDefinition Width="*" />
                                            <ColumnDefinition Width="Auto" />
                                        </Grid.ColumnDefinitions>
 
                                        <Image HeightRequest="50" HorizontalOptions="Center" Source="{Binding ContactImage}" VerticalOptions="Center" WidthRequest="50" />
 
                                        <Grid Grid.Column="1" Padding="10,0,0,0" RowSpacing="1" VerticalOptions="Center">
                                            <Grid.RowDefinitions>
                                                <RowDefinition Height="*" />
                                                <RowDefinition Height="*" />
                                            </Grid.RowDefinitions>
 
                                            <Label LineBreakMode="NoWrap" Text="{Binding ContactName}" TextColor="#474747" />
                                            <Label Grid.Row="1" Grid.Column="0" LineBreakMode="NoWrap" Text="{Binding ContactNumber}" TextColor="#474747" />
                                        </Grid>
                                        <Grid Grid.Row="0" Grid.Column="2" HorizontalOptions="End" RowSpacing="0" VerticalOptions="Start">
 
                                            <Label LineBreakMode="NoWrap" Text="{Binding ContactType}" TextColor="#474747" />
                                        </Grid>
                                    </Grid>
                                </Grid>
                            </DataTemplate>
                        </syncfusion:SfListView.ItemTemplate>
                    </syncfusion:SfListView>
                </autoComplete:SfAutoComplete.DropDownHeaderView>
            </autoComplete:SfAutoComplete>
        </StackLayout>
    </ContentPage.Content>

public MainPage()
        {
            InitializeComponent();
            contactsViewModel = new ContactsViewModel();
            listView.DataSource.GroupDescriptors.Add(new GroupDescriptor()
            {
                PropertyName = "ContactName",
                KeySelector = (object obj1) =>
                {
                    var item = (obj1 as Contacts);
                    return item.ContactName[0].ToString();
                }
            });
 
            listView.SelectionChanged += ListView_SelectionChanged;
            autoComplete.SelectionChanged += AutoComplete_SelectionChanged;
            this.BindingContext = contactsViewModel;
        }