WPF：绑定的数据网格不更新项目属性
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时间：2020-09-13 09:02:50 来源:igfitidea点击:
WPF: Bound datagrid does not update items properties
提问by Oscar Mateu
I'm trying to implement my first MVVM application. I could bound the data in a datagrid, but the changes I make in items does not fire the RaisePropertyChanged method of the Model.
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。
This is My ViewModel
这是我的视图模型
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();
}
}
The Model, implements NotificationObject class that provides the INotifyPropertyChanged
模型，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
}
}
}
And finally, the View:
最后，视图：
<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>
What do I am forgetting or doing wrong?
我忘记了什么或做错了什么？
Thanks in advance!
提前致谢！
Oscar
奥斯卡
采纳答案by Oscar Mateu
Thank you so much Loetn and Andras Seb?, your clues resulted very helpful! The solution below has been which I have adopted and it has worked perfectly!!!
非常感谢 Loetn 和 Andras Seb？，您的线索非常有帮助！下面的解决方案是我采用的，并且效果很好！！！
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
}
回答by Loetn
Bind this event to the CollectionChanged event of your ObservableCollection:
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
}
回答by Andras Sebo
Because the items are in the collection and the collection itself does not change. You have to subscribe in the UsersViewModel class every UserModel changes before you add it to the collection.
因为项目在集合中并且集合本身不会改变。在将每个 UserModel 更改添加到集合之前，您必须在 UsersViewModel 类中订阅它。
Here is a possible solution:
这是一个可能的解决方案：
