我正在尝试实现我的第一个MVVM应用程序。我可以将数据绑定到数据网格中，但是我在项目中所做的更改不会触发模型的RaisePropertyChanged方法。
这是我的ViewModel
public class UsersViewModel : BaseViewModel
{
private static TOPEntities _context;
private ObservableCollection<UserModel> _usersCollection;
public UsersViewModel()
{
_usersCollection = new ObservableCollection<UserModel>(GetAllUsers());
}
public ObservableCollection<UserModel> UsersCollection
{
get { return _usersCollection; }
set
{
if (_usersCollection != value)
{
_usersCollection = value;
RaisePropertyChanged(() => UsersCollection);
}
}
}
public static List<UserModel> GetAllUsers()
{
using (_context = new TOPEntities())
{
return _context.Users.Select
(user => new UserModel
{
Id_User = user.Id_User,
Name = user.Name,
Username = user.Username,
Language = user.Language,
Password = user.Password,
Profile = user.Profile
}).ToList();
}
}
Model，实现了提供INotifyPropertyChanged
的NotificationObject类 public class UserModel : NotificationObject
{
#region Construction
/// Constructs the default instance of a UserModel
public UserModel()
{
}
#endregion
#region Model Attributes
private int _id_User;
private string _username;
private string _password;
private string _profile;
private string _name;
private string _language;
#endregion
#region Properties
public int Id_User
{
get { return _id_User; }
set
{
if (_id_User != value)
{
_id_User = value;
RaisePropertyChanged(() => Id_User);
}
}
}
public string Username
{
get { return _username; }
set
{
if (_username != value)
{
_username = value;
RaisePropertyChanged(() => Id_User);
}
}
}
public string Password
{
get { return _password; }
set
{
if (_password != value)
{
_password = value;
RaisePropertyChanged(() => Id_User);
}
}
}
public string Profile
{
get { return _profile; }
set
{
if (_profile != value)
{
_profile = value;
RaisePropertyChanged(() => Id_User);
}
}
}
public string Name
{
get { return _name; }
set
{
if (_name != value)
{
_name = value;
RaisePropertyChanged(() => Name);
}
}
}
public string Language
{
get { return _language; }
set
{
if (_language != value)
{
_language = value;
RaisePropertyChanged(() => Language);
}
}
}
#endregion
}
}
最后，观点：
<Window x:Class="TOP2.Views.UsersView"
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"
mc:Ignorable="d"
xmlns:viewModels="clr-namespace:TOP2.ViewModels"
xmlns:local="TOP2"
Title="Sample App"
WindowStartupLocation="CenterScreen"
Height="459"
Width="795">
<Window.Resources>
<viewModels:UsersViewModel x:Key="Windows1ViewModel" />
</Window.Resources>
<Grid DataContext="{StaticResource Windows1ViewModel}">
<DataGrid ItemsSource="{Binding UsersCollection, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" AutoGenerateColumns="False" HorizontalAlignment="Left" Margin="81,51,0,0" VerticalAlignment="Top" Height="332" Width="622">
<DataGrid.Columns>
<DataGridTextColumn Binding="{Binding Username, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
<DataGridTextColumn Binding="{Binding Name, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
</DataGrid.Columns>
</DataGrid>
</Grid>
我忘记或做错了什么？
提前致谢！
的奥斯卡
答案 0 :(得分：5)
非常感谢Loetn和AndrasSebö，你的线索非常有帮助！下面的解决方案已经采用了，它已经完美运行了!!!
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel; // ObservableCollection
using System.ComponentModel; // INotifyPropertyChanged
using System.Collections.Specialized; // NotifyCollectionChangedEventHandler
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ObservableCollectionTest
{
class Program
{
static void Main(string[] args)
{
// ATTN: Please note it's a "TrulyObservableCollection" that's instantiated. Otherwise, "Trades[0].Qty = 999" will NOT trigger event handler "Trades_CollectionChanged" in main.
// REF: http://stackoverflow.com/questions/8490533/notify-observablecollection-when-item-changes
TrulyObservableCollection<Trade> Trades = new TrulyObservableCollection<Trade>();
Trades.Add(new Trade { Symbol = "APPL", Qty = 123 });
Trades.Add(new Trade { Symbol = "IBM", Qty = 456});
Trades.Add(new Trade { Symbol = "CSCO", Qty = 789 });
Trades.CollectionChanged += Trades_CollectionChanged;
Trades.ItemPropertyChanged += PropertyChangedHandler;
Trades.RemoveAt(2);
Trades[0].Qty = 999;
Console.WriteLine("Hit any key to exit");
Console.ReadLine();
return;
}
static void PropertyChangedHandler(object sender, PropertyChangedEventArgs e)
{
Console.WriteLine(DateTime.Now.ToString() + ", Property changed: " + e.PropertyName + ", Symbol: " + ((Trade) sender).Symbol + ", Qty: " + ((Trade) sender).Qty);
return;
}
static void Trades_CollectionChanged(object sender, EventArgs e)
{
Console.WriteLine(DateTime.Now.ToString() + ", Collection changed");
return;
}
}
#region TrulyObservableCollection
public class TrulyObservableCollection<T> : ObservableCollection<T>
where T : INotifyPropertyChanged
{
public event PropertyChangedEventHandler ItemPropertyChanged;
public TrulyObservableCollection()
: base()
{
CollectionChanged += new NotifyCollectionChangedEventHandler(TrulyObservableCollection_CollectionChanged);
}
void TrulyObservableCollection_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
if (e.NewItems != null)
{
foreach (Object item in e.NewItems)
{
(item as INotifyPropertyChanged).PropertyChanged += new PropertyChangedEventHandler(item_PropertyChanged);
}
}
if (e.OldItems != null)
{
foreach (Object item in e.OldItems)
{
(item as INotifyPropertyChanged).PropertyChanged -= new PropertyChangedEventHandler(item_PropertyChanged);
}
}
}
void item_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
NotifyCollectionChangedEventArgs a = new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset);
OnCollectionChanged(a);
if (ItemPropertyChanged != null)
{
ItemPropertyChanged(sender, e);
}
}
}
#endregion
#region Sample entity
class Trade : INotifyPropertyChanged
{
protected string _Symbol;
protected int _Qty = 0;
protected DateTime _OrderPlaced = DateTime.Now;
public DateTime OrderPlaced
{
get { return _OrderPlaced; }
}
public string Symbol
{
get
{
return _Symbol;
}
set
{
_Symbol = value;
NotifyPropertyChanged("Symbol");
}
}
public int Qty
{
get
{
return _Qty;
}
set
{
_Qty = value;
NotifyPropertyChanged("Qty");
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(String propertyName = "")
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
#endregion
}
答案 1 :(得分：3)
将此事件绑定到ObservableCollection的CollectionChanged事件：
private void ObservableCollection_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
if (e.NewItems != null)
{
foreach (var item in e.NewItems)
{
item.PropertyChanged += this.Item_PropertyChanged;
}
}
if (e.OldItems != null)
{
foreach (var item in e.OldItems)
{
item.PropertyChanged -= this.Item_PropertyChanged;
}
}
}
private void Item_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
// do something
}
答案 2 :(得分：2)
因为项目在集合中，集合本身不会更改。在将UserModel添加到集合之前，您必须在UsersViewModel类中订阅每个UserModel。
这是一个可能的解决方案：