wpf datarow绑定正在保存更改，但不能插入或删除

Question

I'm new to wpf so this is a learning curve to me. I have the binding working, so any update I do works without an issue.

The problem is the adds and deletes. Neither of them work.

Here is my code:

using System;
using System.Linq;
using System.Windows;
using WebPortalSourceId.data;

namespace WebPortalSourceId
{
  public partial class MainWindow : Window
  {
    private Guid _corporationId;

    private SuburbanPortalEntities entity;
    public MainWindow()
    {
      InitializeComponent();
      entity = new SuburbanPortalEntities();
    }

    private void Search_Click(object sender, RoutedEventArgs e)
    {
      if (CompanyCode.Text.Length != 3)
      {
        MessageBox.Show("Invalid Company Code. It must be 3 characters in length.");
        return;
      }
      _corporationId = GetCorporationId(CompanyCode.Text.ToUpper());
      FillDataGrid(_corporationId);
    }

    public void FillDataGrid(Guid corporationId)
    {
      var query = from s in entity.Sources where s.CorporationId == corporationId select s;  
      if (query.Any())
      {
        SourceDataGrid.ItemsSource = query.ToList();
      }    
      SourceDataGrid.Columns[2].Visibility = Visibility.Hidden;
      SourceDataGrid.Columns[0].IsReadOnly = true;
      SourceDataGrid.Columns[1].IsReadOnly = true;

    }

    private Guid GetCorporationId(string companycode)
    {
        return (from cs in entity.CorporationStructures
          where cs.Company == companycode &
                cs.IsActive & 
                cs.Branch == null
          select cs.CorporationId).FirstOrDefault();
    }

    private void Save_Click(object sender, RoutedEventArgs e)
    {
      entity.SaveChanges();
    }

    private void SourceDataGrid_AddingNewItem(object sender, System.Windows.Controls.AddingNewItemEventArgs e)
    {
      var sources = new Source();
      sources.CorporationId = _corporationId;
      sources.Description = string.Empty;
      sources.IsActive = true;
      sources.Name = string.Empty;
      sources.SourceId = Guid.NewGuid();
      sources.TokenId = Guid.NewGuid();
      e.NewItem = sources;
    }

  }

}

And my xaml:

<Window x:Class="WebPortalSourceId.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Web Portal SourceId" Height="475" Width="948" WindowStartupLocation="CenterScreen" ResizeMode="NoResize">
  <Grid>
    <TextBox Name="CompanyCode" HorizontalAlignment="Left" Height="23" Margin="337,11,0,0" TextWrapping="Wrap" Text="" VerticalAlignment="Top" Width="48" MaxLength="3" TextAlignment="Center" CharacterCasing="Upper"/>
    <Label Content="Company Code" HorizontalAlignment="Left" Margin="240,10,0,0" VerticalAlignment="Top"/>
    <DataGrid Name="SourceDataGrid" Margin="10,43,10,10" CanUserReorderColumns="False" CanUserResizeRows="False" HorizontalContentAlignment="Stretch" FontFamily="Microsoft YaHei" AddingNewItem="SourceDataGrid_AddingNewItem" SelectionMode="Single" SelectionUnit="CellOrRowHeader"/>
    <Button Name="Search" Content="Search" HorizontalAlignment="Left" Margin="390,11,0,0" VerticalAlignment="Top" Width="75" Height="23" Click="Search_Click"/>
    <Button x:Name="Save" Content="Save" Margin="470,11,397,0" VerticalAlignment="Top" Height="23" Click="Save_Click" HorizontalContentAlignment="Center"/>


  </Grid>
</Window>

What am I missing?

Answer 1

public void FillDataGrid(Guid corporationId)
{
  var query = from s in entity.Sources where s.CorporationId == corporationId select s;
  query.Load(); 

  SourceDataGrid.ItemsSource = entity.Sources.Local;  
  SourceDataGrid.Columns[2].Visibility = Visibility.Hidden;
  SourceDataGrid.Columns[0].IsReadOnly = true;
  SourceDataGrid.Columns[1].IsReadOnly = true;

}

Queryable<T>.ToList() creates a List that Entity Framework knows nothing about. However EF still keeps a reference to each SourceProxy item it instanciated from the database.

By using DbSet<T>.Local we get an ObservableCollection , which EF has bound to for inserts and deletes. However be advised, it is fracking slow. Not to mention, all access to it now must be done via the UI thread.

So even DB access to DbSet<T> must be done via the UI thread. Which is bad.

A better way to deal with this is to create you own ObservableCollection , and handle the Remove / Add yourself.