value from listview passed to popup

I am trying to pass the information from a listview to a popup form and I can see the data sitting in SelectedItem and unable to get it out. Thanks for your help.

               <ListView HeightRequest="150" x:Name="listPost" ItemsSource="{Binding myRatingList}" ItemSelected="OnOpenRatingPupup">
                            <ListView.ItemTemplate>
                                <DataTemplate>
                                    <ViewCell>
                                        <StackLayout Orientation="Horizontal">
                                            <Label Text="{Binding ScoreDesc}" x:Name="lblScoreDesc"  TextColor="Black" Margin="8,0,0,0" VerticalTextAlignment="Center"></Label>
                                            <StackLayout HorizontalOptions="EndAndExpand" VerticalOptions="Center">
                                                <rating:RadShapeRating x:Name="xRating" Value="{Binding Value}" IsEnabled="false"></rating:RadShapeRating>
                                            </StackLayout>
                                            <Label Text="{Binding Comment}" x:Name="lblComment"  TextColor="Black" Margin="8,0,0,0"></Label>
                                        </StackLayout>
                                    </ViewCell>
                                </DataTemplate>
                            </ListView.ItemTemplate>
                        </ListView>

.cs file - dataItem is null

 public class postlist_model {
            public string Comment { get; set; }
            public string ScoreDesc { get; set; }
            public string Value { get; set; }
        }

    private async void OnOpenRatingPupup(object sender, SelectedItemChangedEventArgs e)
    {
        if (e.SelectedItem == null) {
            return;
        }

        var dataItem = e.SelectedItem as postlist_model;

        if (dataItem == null) {
            return;
        }

        var page = new RatingsPopup(InTradeShowID, "Booth Site", "1");
        await Navigation.PushPopupAsync(page);
    }

If I preview e.SelectedItem it lists the values Comment=""; ScoreDesc="Booth Site", Value="0".