如何检测我的ObservableCollection中的项是否已更改

I have a datagrid which is bound to ObservableCollection<Product>. When the grid is updated this automatically updates the Product object in my collection.

我有一个绑定到ObservableCollection 的数据网格。更新网格后，这会自动更新集合中的Product对象。

What I want to do now is to have some sort of even that is triggered when any object in the collection is updated -or- some sort of binding to the collection that will return true/false depedant on if any Product has been updated.

我现在要做的是在集合中的任何对象被更新时触发某种甚至触发 - 或者 - 某种类型的绑定到集合，如果任何产品已经更新，它将返回真/假的depedant。

The overall objective is to have a save button on my main window that is disabled if no changes have been made to my collection and enabled if changes have been made.

总体目标是在我的主窗口上有一个保存按钮，如果没有对我的集合进行任何更改，则该按钮被禁用，如果已经进行了更改，则启用该按钮。

I have read into INotifyPropertyChange but I dont see how I can use this to monitor changes on a whole collection.

我已经阅读了INotifyPropertyChange，但我没有看到我如何使用它来监控整个集合的变化。

Additionally, if I implement this interface on my Product class I dont see how my UI can monitor every product in the collection - or can it?

另外，如果我在我的Product类上实现这个接口，我不会看到我的UI如何监视集合中的每个产品 - 或者它可以吗？

4 个解决方案

#1

Implement INotifyPropertyChanged in your Product class with notification for every property.
在Product类中实现INotifyPropertyChanged，并为每个属性提供通知。
Implement INotifyPropertyChanged in your viewmodel.
在viewmodel中实现INotifyPropertyChanged。
Add property IsDirty to your ViewModel (with notification through INotifyPropertyChanged.
将属性IsDirty添加到ViewModel（通过INotifyPropertyChanged通知。

In your viewmodel, subscribe to CollectionChanged

在您的viewmodel中，订阅CollectionChanged

public YourViewModel()
{
    ...
    YourCollection.CollectionChanged += YourCollection_CollectionChanged; 
    ...
}

private void YourCollection_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs args)
{
    if (args.OldItems != null)
        foreach(var oldItem in args.OldItems)
            oldItem.PropertyChanged -= YourItem_PropertyChanged;

    if (args.NewItems != null)
        foreach(var newItem in args.NewItems)
            newItem.PropertyChanged += YourItem_PropertyChanged;
}

private void Youritem_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs args)
{
    IsDirty = true;
}

Now you can bind to IsDirty property of your viewmodel, for example, you can bind Button.IsEnabled property directly to it.

现在您可以绑定到viewmodel的IsDirty属性，例如，您可以将Button.IsEnabled属性直接绑定到它。

#2

Just use the ObservableCollection. It has an event called CollectionChanged. If you register it, you can do what you want. Example:

只需使用ObservableCollection。它有一个名为CollectionChanged的事件。如果你注册它，你可以做你想要的。例：

ObservableCollection<string> strings = new ObservableCollection<string>();
strings.CollectionChanged += new System.Collections.Specialized.NotifyCollectionChangedEventHandler(changed);
strings.Add("Hello");
strings[0] = "HelloHello";

And:

和：

private void changed(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs args)
{
    //You get notified here two times.
}

#3

The logic needs to go in your Model (Product class). A clean approach would be to expose IsDirty property (backed by field) in your model.

逻辑需要进入您的模型（产品类）。一种干净的方法是在模型中公开IsDirty属性（由字段支持）。

And your ViewModel would have a Command binding with CanSave checking the internal collection, and return true if Any of the item in collection IsDirty=true.

并且您的ViewModel将使用CanSave的Command绑定检查内部集合，如果集合中的任何项目IsDirty = true，则返回true。

#4

I think subscribing to the PropertyChanged event for each of the objects in your collection and firing this event, for example, in the setter of your objects can work.

我认为为集合中的每个对象订阅PropertyChanged事件并触发此事件，例如，在对象的setter中可以工作。

However, I think you don't need to do all this to figure out if a cell is changed in your grid. I think you can do something like what they do here instead:

但是，我认为您不需要做所有这些来确定您的网格中是否更改了单元格。我认为你可以做类似他们在这里做的事情：

http://social.msdn.microsoft.com/Forums/en/wpf/thread/81131225-90fb-40f9-a311-066952c7bc43

#1

Implement INotifyPropertyChanged in your Product class with notification for every property.
在Product类中实现INotifyPropertyChanged，并为每个属性提供通知。
Implement INotifyPropertyChanged in your viewmodel.
在viewmodel中实现INotifyPropertyChanged。
Add property IsDirty to your ViewModel (with notification through INotifyPropertyChanged.
将属性IsDirty添加到ViewModel（通过INotifyPropertyChanged通知。