How To Customize Xamarin.Forms Listview Group Header Template In MVVM ?

<ContentPage.Resources>
        <ResourceDictionary>
            <DataTemplate x:Name="GroupHeaderTemplate"  x:Key="GroupHeaderTemplate">
                <ViewCell>
                    <ViewCell.View>
                        <Grid>
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="30" />
                                <ColumnDefinition Width="*" />
                                <ColumnDefinition Width="40" />
                            </Grid.ColumnDefinitions>
                            <Image x:Name="NormalImage" Grid.Column="0" HorizontalOptions="Center"
                        Source="{Binding IsExpand, Converter={StaticResource BoolToImageConverter}}"
                        VerticalOptions="Center"/>
                            <Label x:Name="label" Text="{Binding Key}" Grid.Column="1" 
                        IsVisible="{Binding Path=BindingContext.IsLabelVisible,
                        Source={x:Reference listView}}"/>
                        </Grid>
                    </ViewCell.View>
                </ViewCell>
            </DataTemplate>
        </ResourceDictionary>
</ContentPage.Resources>
<Grid>
    <syncfusion:SfListView x:Name="listView"
                            GroupHeaderTemplate="{StaticResource GroupHeaderTemplate}"                                   
                            ItemsSource="{Binding contactsinfo}">
        <syncfusion:SfListView.ItemTemplate>
            <DataTemplate>
                <ViewCell>
                    <ViewCell.View>
                        <Grid x:Name="grid" RowSpacing="1">
                            <Grid.RowDefinitions>
                                <RowDefinition Height="*" />
                                <RowDefinition Height="1" />
                            </Grid.RowDefinitions>
                            <Grid RowSpacing="1">
                                <Grid>
                                    <Image Source="{Binding ContactImage}"
                                            VerticalOptions="Center"
                                            HorizontalOptions="Center"
                                            HeightRequest="50"/>
                                </Grid>

                                <Grid Grid.Column="1"
                                        RowSpacing="1"
                                        Padding="10,0,0,0"
                                        VerticalOptions="Center">
                                    <Grid.RowDefinitions>
                                        <RowDefinition Height="*" />
                                        <RowDefinition Height="*" />
                                    </Grid.RowDefinitions>

                                    <Label LineBreakMode="WordWrap"
                                            TextColor="#474747"
                                            Text="{Binding ContactName}">
                                    </Label>
                                    <Label Grid.Row="1"
                                            Grid.Column="0"
                                            TextColor="#474747"

                                            Text="{Binding ContactNumber}">
                                    </Label>
                                </Grid>
                            </Grid>
                            <StackLayout Grid.Row="1" BackgroundColor="Gray" HeightRequest="1"/>
                        </Grid>
                    </ViewCell.View>
                </ViewCell>
            </DataTemplate>
        </syncfusion:SfListView.ItemTemplate>
    </syncfusion:SfListView>
</Grid>