[英]Raising event when Property in ObservableCollection changes
I want to raise an Event when a Property in a DataGrid is changed to check if it is valid, save it back to my source file, etc. 我想在更改DataGrid中的属性以检查其是否有效,将其保存回我的源文件等时引发一个事件。
Background Information: I have a DataGrid which is bound to an Observable Collection. 背景信息:我有一个绑定到Observable集合的DataGrid。 At this point I have successfully bound my Observable Collection to the view, however I haven't managed to raise an Event upon Property changes.
至此,我已经成功将Observable Collection绑定到视图,但是在Property更改时我还没有引发一个Event。 Two Way binding also works as i could observe changes to the Collection via debugging.
双向绑定也可以工作,因为我可以通过调试观察Collection的更改。 I'm inheriting INotifyPropertyChanged through BindableBase(Prism).
我正在通过BindableBase(Prism)继承INotifyPropertyChanged。
public ObservableCollection<CfgData> Cfg
{
get { return _cfg; }
set { SetProperty(ref _cfg, value); }
}
private ObservableCollection<CfgData> _cfg;
CfgData contains 4 Properties: CfgData包含4个属性:
public class CfgData
{
public string Handle { get; set; }
public string Address { get; set; }
public string Value { get; set; }
public string Description { get; set; }
public CfgData(string handle, string address, string value)
{
this.Handle = handle;
this.Address = address;
this.Value = value;
}
public CfgData(string handle, string address, string value, string description)
{
this.Handle = handle;
this.Address = address;
this.Value = value;
this.Description = description;
}
}
I am populating my Observable Collection with Values read from a csv. 我正在用从csv读取的值填充我的Observable集合。 file
文件
public ObservableCollection<CfgData> LoadCfg(string cfgPath)
{
var cfg = new ObservableCollection<CfgData>();
try
{
using (var reader = new StreamReader(cfgPath))
{
while (!reader.EndOfStream)
{
var line = reader.ReadLine();
var values = line.Split(';');
if (values.Length == 3)
{
cfg.Add(new CfgData(values[0], values[1], values[2]));
}
else if (values.Length == 4)
{
cfg.Add(new CfgData(values[0], values[1], values[2], values[3]));
}
}
}
}
catch (Exception x)
{
log.Debug(x);
}
return cfg;
}
My XAML 我的XAML
<DataGrid Name="cfgDataGrid" Margin="10,10,109,168.676" ItemsSource="{Binding Cfg, Mode=TwoWay}" AutoGenerateColumns="False"> <DataGrid.Columns> <DataGridTextColumn Header="Handle" Binding="{Binding Path=Handle}" Width="auto" IsReadOnly="True" /> <DataGridTextColumn Header="Address" Binding="{Binding Path=Address}" Width="auto" IsReadOnly="True" /> <DataGridTextColumn Header="Value" Binding="{Binding Path=Value}" Width="auto" IsReadOnly="False" /> <DataGridTextColumn Header="Description" Binding="{Binding Path=Description}" Width="auto" IsReadOnly="True" /> </DataGrid.Columns> </DataGrid>
The Problem 2 way binding updates the collection in my viewmodel. 问题 2方式绑定更新了我的视图模型中的集合。 However i would like to verify the input before saving it.
但是我想在保存之前验证输入。 I would also like to be able to add some functionality like calling a method when an edit is verified.
我还希望能够添加一些功能,例如在验证编辑后调用方法。 Therefore I have attempted to use several event handling ways like
因此,我尝试使用几种事件处理方式,例如
this.Cfg.CollectionChanged += new NotifyCollectionChangedEventHandler(Cfg_OnCollectionChanged);
or 要么
this.Cfg.CollectionChanged += Cfg_OnCollectionChanged;
however those never called the functions when i changed the datagrid. 但是,当我更改数据网格时,那些从未调用过的函数。
The Questions How do i create an event handler that gets called upon a Property change? 问题我如何创建在属性更改时被调用的事件处理程序? Do i have to save back the whole set of Data or can i save back just the changed datarow/property?
我必须保存整个数据集还是可以只保存更改后的数据行/属性?
Because ObservableCollection
doesn't observe his items. 因为
ObservableCollection
没有观察他的项目。 It will raise an event for an insert, delete an item, or reset the collection, not a modification on his item. 它将引发插入事件,删除项目或重置集合,而不是对其项目进行修改。
So, you must implement ObservableCollection
which observe equally his items. 因此,您必须实现
ObservableCollection
,它平等地观察他的项目。 This code used in my project found on SO but I can't figure out the post original. 我的项目中使用的这段代码可以在SO上找到,但是我无法弄清楚帖子的原件。 When we add the new item to the collection, it adds an INotifyPropertyChanged event for it.
当我们将新项目添加到集合时,它将为其添加INotifyPropertyChanged事件。
public class ItemsChangeObservableCollection<T> :
System.Collections.ObjectModel.ObservableCollection<T> where T : INotifyPropertyChanged
{
protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
{
if (e.Action == NotifyCollectionChangedAction.Add)
{
RegisterPropertyChanged(e.NewItems);
}
else if (e.Action == NotifyCollectionChangedAction.Remove)
{
UnRegisterPropertyChanged(e.OldItems);
}
else if (e.Action == NotifyCollectionChangedAction.Replace)
{
UnRegisterPropertyChanged(e.OldItems);
RegisterPropertyChanged(e.NewItems);
}
base.OnCollectionChanged(e);
}
protected override void ClearItems()
{
UnRegisterPropertyChanged(this);
base.ClearItems();
}
private void RegisterPropertyChanged(IList items)
{
foreach (INotifyPropertyChanged item in items)
{
if (item != null)
{
item.PropertyChanged += new PropertyChangedEventHandler(item_PropertyChanged);
}
}
}
private void UnRegisterPropertyChanged(IList items)
{
foreach (INotifyPropertyChanged item in items)
{
if (item != null)
{
item.PropertyChanged -= new PropertyChangedEventHandler(item_PropertyChanged);
}
}
}
private void item_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
//launch an event Reset with name of property changed
base.OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
}
}
}
Next, your model 接下来,你的模型
private ItemsChangeObservableCollection<CfgData> _xx = new ItemsChangeObservableCollection<CfgData>();
public ItemsChangeObservableCollection<CfgData> xx
{
get { return _xx ;}
set { _xx = value; }
}
Last but not least, your model must implement INotifyPropertyChanged
最后但并非最不重要的一点是,您的模型必须实现
INotifyPropertyChanged
public class CfgData: INotifyPropertyChanged
{
}
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