Binding entity into WPF datagrid with EF 7 (core)

Question

I have a simple problem with data binding. I'm not able to get the datagrid DeviceDataGrid to visualise the entity information. The MainWindow.xaml file is as follows:

<Window 
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:domain="clr-namespace:FxEditorDatabaseStructure.Core.Domain"
    mc:Ignorable="d" x:Class="FxEditorDatabaseStructure.MainWindow"
        Title="MainWindow" Height="350" Width="525" Loaded="Window_Loaded">
    <Window.Resources>
        <CollectionViewSource x:Key="DeviceViewSource" d:DesignSource="{d:DesignInstance {x:Type domain:Device}, CreateList=True}"/>
    </Window.Resources>
    <Grid DataContext="{StaticResource DeviceViewSource}">
        <DataGrid x:Name="DeviceDataGrid" AutoGenerateColumns="False" EnableRowVirtualization="True" ItemsSource="{Binding}" Margin="0,64,0,0" RowDetailsVisibilityMode="VisibleWhenSelected">
            <DataGrid.Columns>
                <DataGridTextColumn x:Name="NameColumn" Binding="{Binding Name}" Header="Name" Width="250"/>
                <DataGridTextColumn x:Name="SocketCountColumn" Binding="{Binding DeviceId}" Header="Id" Width="Auto"/>
                <DataGridTextColumn x:Name="DescriptionColumn" Binding="{Binding Description}" Header="Description" Width="Auto"/>
                <DataGridTextColumn x:Name="ProductTypeColumn" Binding="{Binding ProductType}" Header="Product Type" Width="*"/>
            </DataGrid.Columns>
        </DataGrid>
        <Button Content="Add" HorizontalAlignment="Left" Margin="23,25,0,0" VerticalAlignment="Top" Width="75" RenderTransformOrigin="-0.143,-0.057" Click="AddDevice_Click"/>
    </Grid>
</Window>

And trying to visualise the data within the entity on MainWindow. The database is correctly created and even the add button works. This I am able to see with Firefox SQLite Manager.

Here is the xaml.cs file which is "binding" the entity into the datagrid after eager loading entities into memory:

    public partial class MainWindow : Window
    {
        private FxContext _context = new FxContext();

        public MainWindow()
        {
            InitializeComponent();
            _context.Database.Migrate();
        }
        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            _context.Devices.Add(new Device
            {
                ProductCode = "100",
                Name = "LUX999",
                Description = "Measurement device",
                Supplier = "X",
                Category = "Sensors",
                ProductType = "Field device",
                TimeCreated = DateTime.Now
            });
            _context.SaveChanges();

            System.Windows.Data.CollectionViewSource deviceViewSource = ((System.Windows.Data.CollectionViewSource)(this.FindResource("DeviceViewSource")));
            _context.Devices.Load();
            _context.Sockets.Load();
            _context.ProductTypes.Load();
            deviceViewSource.Source = _context.Devices.GetLocal();
            deviceViewSource.Source = _context.Categories.GetLocal();
            deviceViewSource.Source = _context.ProductTypes.GetLocal();
        }

        protected override void OnClosing(System.ComponentModel.CancelEventArgs e)
        {
            base.OnClosing(e);

            _context.Dispose();
        }

        private void AddDevice_Click(object sender, RoutedEventArgs e)
        {
            _context.Devices.Add(
                new Device
                {
                    TimeCreated = DateTime.Now,
                    Name = "New Device at " + DateTime.Now.ToShortDateString()
                });

            _context.SaveChanges();
        }
    }
}

Because the EF7 (core) still lacks the implementation of local() I'm using an alternative extension method.

public static class Extensions
{
    public static ObservableCollection<TEntity> GetLocal<TEntity>(this DbSet<TEntity> set)
        where TEntity : class
    {
        var context = set.GetService<DbContext>();
        var data = context.ChangeTracker.Entries<TEntity>().Select(e => e.Entity);
        var collection = new ObservableCollection<TEntity>(data);

        collection.CollectionChanged += (s, e) =>
        {
            if (e.NewItems != null)
            {
                context.AddRange(e.NewItems.Cast<TEntity>());
            }

            if (e.OldItems != null)
            {
                context.RemoveRange(e.OldItems.Cast<TEntity>());
            }
        };

        return collection;
    }
}

When I run the application the datagrid is not showing any values from the database in its list view. Somehow this line is not transferring the entity correctly deviceViewSource.Source = _context.Devices.GetLocal(); OR some binding procedure is wrong in the xaml-file?

Any ideas what I'm doing wrong?

Answer 1

The problem is, that you set deviceViewSource.Source to devices, then replaced with Categories, then with ProductTypes

deviceViewSource.Source = _context.Devices.GetLocal();
deviceViewSource.Source = _context.Categories.GetLocal();
deviceViewSource.Source = _context.ProductTypes.GetLocal();

at the and, you are databanding to ProductTypes... Remove the two bottom lines.

I believe that you dont need the GetLocal() method neither. Try this:

deviceViewSource.Source = _context.Devices