为什么我未在预览中显示来自Firebase的数据

Question

我可以从Firebase以后的数据库中看到我的数据，因为我在部署时在previsualizer中没有看到它正常吗？我很确定这不是显示数据的正确方法，但这是我唯一做过的方法

添加正确的行以添加伪造的Itmes但不起作用

print capture

---

xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup- 
compatibility/2006"
d:DataContext="{d:DesignInstance x:Object}"
mc:Ignorable="d

---

 <ListView x:Name="listIdeas"
                  ItemTapped="OnItemSelected">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <!--<TextCell Detail="{Binding Titre}" Text="{Binding Description}" />-->
                    <ViewCell x:Name="listIdeas">
                        <Grid Padding="10" RowSpacing="10" ColumnSpacing="10">
                            <Grid.RowDefinitions>
                                <RowDefinition Height="60"/>
                                <RowDefinition Height="Auto"/>
                            </Grid.RowDefinitions>
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="90*"/>
                                <ColumnDefinition Width="10*"/>
                            </Grid.ColumnDefinitions>

                            <Label Grid.Column="0" Text="{Binding Titre}" HorizontalOptions="Start"/>
                            <Label Grid.Column="1" Text="{Binding Vote}" HorizontalOptions="End"/>
                        </Grid>
                    </ViewCell>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>

 // xaml.CS
 protected async override void OnAppearing()
    {
        base.OnAppearing();
        var allIdeas = await firebaseHelper.GetAllIdeas();
        listIdeas.ItemsSource = allIdeas;
    }

 // Helpers
 FirebaseClient firebase = new 
 FirebaseClient("https://xxx.firebaseio.com/");

    public async Task<List<ItemsModel>> GetAllIdeas()
    {

        return (await firebase
          .Child("Ideas")
          .OnceAsync<ItemsModel>()).Select(item => new ItemsModel
          {
              Titre = item.Object.Titre,
              Description = item.Object.Description,
              Vote = item.Object.Vote
          }).ToList();
    }