Hi all I have a page that I'm trying to ADD to a list and save it with viewmodel and SQL. but my list is empty Can you tell me where am I wrong?? on my Xaml (Page1): my Model (Energypage): And on my EnergyViewModel: I did bond my page1 to Energyviewmodel, and it works find when I didn't use

Saving with SQL

Hi all I have a page that I’m trying to ADD to a list and save it with viewmodel and SQL. but my list is empty Can you tell me where am I wrong??

on my Xaml (Page1):

<Entry Margin="5" Text="{Binding Xname}"  Grid.Row="1" Grid.Column="0" Grid.ColumnSpan="2" FontSize="16" x:Name="entry1" Placeholder="Enter X-rays (6 MV)" PlaceholderColor="White"  BackgroundColor="Gray"/>

<Button Grid.Column="0"
                         Grid.Row="2"
                  FontAttributes="Bold"
                 
                  Command="{Binding AddXrayCommand}"
                        
                  Text="Add" />

            <ListView Grid.Row="3" Grid.ColumnSpan="2" HasUnevenRows="True" Margin="40"
                      ItemsSource="{Binding energyX}" SelectedItem="{Binding selecteditemX}" 
                    HorizontalOptions="Start" WidthRequest="150" >
                <ListView.ItemTemplate>
                    <DataTemplate>
                        <ViewCell>
                            <Grid>
                                <Grid.RowDefinitions>
                                    <RowDefinition Height="30"></RowDefinition>
                                    <RowDefinition Height="5"></RowDefinition>
                                </Grid.RowDefinitions>
                                <Grid.ColumnDefinitions>

                                </Grid.ColumnDefinitions>

                                <Label Grid.Row="0" BackgroundColor="White" Text="{Binding xray}" FontSize="Large" HorizontalTextAlignment="Center" TextColor="Black" WidthRequest="35"/>
                                <Frame Grid.Row="1" BackgroundColor="Gray"></Frame>
                            </Grid>

                        </ViewCell>
                    </DataTemplate>
                </ListView.ItemTemplate>
            </ListView>

my Model (Energypage):

public class EnergyX
    {
        [PrimaryKey, AutoIncrement]

        public int Id { get; set; }
        public string xray { get; set; }

    }

And on my EnergyViewModel:

public class EnergyViewModel
    {
        public SQLiteConnection conn;

        public ObservableCollection<EnergyX> energyX { get; set; } = new ObservableCollection<EnergyX>();
        public string Xname { get; set; }

        public ICommand AddXrayCommand => new Command(AddX);


        public SQLiteConnection GetSQLiteConnection()
        {
            var fileName = "Energys.db";

            var documentPath = System.Environment.GetFolderPath(System.Environment.SpecialFolder.LocalApplicationData);

            var path = Path.Combine(documentPath, fileName);

            var connection = new SQLiteConnection(path);

            return connection;
        }



        public void AddX()
        {
            if (Xname != null && Xname.Length > 0)
            {
                EnergyX XX = new EnergyX();

                
                XX.xray = Xname;

                
                conn = GetSQLiteConnection();

               conn.CreateTable<EnergyX>(); 

               var dataX = conn.Table<EnergyX>();
               var resultX = conn.Insert(XX);

               


                energyX = new ObservableCollection<EnergyX>(conn.Table<EnergyX>().ToList());

               

            }

        }

    }
}

I did bond my page1 to Energyviewmodel, and it works find when I didn’t use SQL service, I think my SQL has problem…

I have debug the viewmodel and program run to the end of the Viewmodel but my xaml page list is empty.

Answer

this line creates a completely new instance of energyX when your ListView is bound to the old instance

energyX = new ObservableCollection(conn.Table().ToList());

there are two ways you could fix this

option 1, use INotifyPropertyChanged and raise a PropertyChanged event in the setter of energyX

option 2, don’t create a new instance of energyX. Instead just add the new item to the existing instance

energyX.Add(XX);

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Answer