wpf 属性改变时的WPF调用方法

WPF call method when property changes

提问by mauryat

In C#, how can a method be called when a property changes (both method and property belong to the same class)?

在C#中，如何在属性改变时调用方法（方法和属性都属于同一个类）？

e.g.,

例如，

class BrowserViewModel
{
    #region Properties

    public List<TreeViewModel> Status { get; private set; }
    public string Conditions { get; private set; }

    #endregion // Properties

    // i'd like to call this method when Status gets updated
    void updateConditions
    {
         /* Conditions = something depending on the TreeViewItem select status */
    }
}

Binding

捆绑

<TreeView Grid.Row="1"
    x:Name="StatusTree"
    ItemContainerStyle="{StaticResource TreeViewItemStyle}"
    ItemsSource="{Binding Path=Status, Mode=OneTime}"
    ItemTemplate="{StaticResource CheckBoxItemTemplate}"
/>

Use-Case(if you are curious)

用例（如果你好奇的话）

The property Statusis bound to a TreeViewcontrol in the xaml. When it is updated, I'd like to call a method that updates the property Conditions. This property is bound to a TextBoxin the xaml.

该属性Status绑定到TreeViewxaml 中的控件。当它更新时，我想调用一个更新属性的方法Conditions。此属性绑定到TextBoxxaml 中的 a。

I'm new to Eventing in C#, so am a little lost.

我是 C# 中的 Eventing 新手，所以有点迷茫。

Edit

编辑

1. class TreeViewModelimplements INotifyPropertyChanged.
2. Conditionsis updated by getting the IsCheckedValue from the TreeView.
3. The size of the Status List never changes. When a TreeViewItem is selected/unselected the TreeViewModel changes.
4. TreeViewModel source (FooViewModel on thispage)
5. Binding code above.

6. Didn't have to change Binding Mode for IsChecked.

       <HierarchicalDataTemplate 
           x:Key="CheckBoxItemTemplate"
           ItemsSource="{Binding Children, Mode=OneTime}"
           >
               <StackPanel Orientation="Horizontal">
               <!-- These elements are bound to a TreeViewModel object. -->
               <CheckBox
                   Focusable="False" 
                   IsChecked="{Binding IsChecked}" 
                   VerticalAlignment="Center"
                   />
               <ContentPresenter 
                   Content="{Binding Name, Mode=OneTime}" 
                   Margin="2,0"
                   />
               </StackPanel>
       </HierarchicalDataTemplate>
   

1. 类TreeViewModel实现INotifyPropertyChanged.
2. Conditions通过IsChecked从TreeView.
3. 状态列表的大小永远不会改变。When a TreeViewItem is selected/unselected the TreeViewModel changes.
4. TreeViewModel源（FooViewModel在此页）
5. 上面的绑定代码。

6. 不必更改 .bin 的绑定模式IsChecked。

       <HierarchicalDataTemplate 
           x:Key="CheckBoxItemTemplate"
           ItemsSource="{Binding Children, Mode=OneTime}"
           >
               <StackPanel Orientation="Horizontal">
               <!-- These elements are bound to a TreeViewModel object. -->
               <CheckBox
                   Focusable="False" 
                   IsChecked="{Binding IsChecked}" 
                   VerticalAlignment="Center"
                   />
               <ContentPresenter 
                   Content="{Binding Name, Mode=OneTime}" 
                   Margin="2,0"
                   />
               </StackPanel>
       </HierarchicalDataTemplate>
   

回答by Conrad Clark

I assume you want updateConditionsto fire whenever an itemis added/removed/changed in your list, not if the list reference itself changes.

我假设您想在列表中添加/删除/更改updateConditionsan 时触发item，而不是在列表引用本身发生更改时触发。

Since you're implementing INotifyPropertyChanged within your TreeViewModel, I think you'll want to use ObservableCollection<T>instead of a plain List<T>. Check it here: http://msdn.microsoft.com/en-us/library/ms668604.aspx

由于您在 TreeViewModel 中实现 INotifyPropertyChanged，我认为您会想要使用ObservableCollection<T>而不是普通的List<T>. 在这里检查：http: //msdn.microsoft.com/en-us/library/ms668604.aspx

Represents a dynamic data collection that provides notifications when items get added, removed, or when the whole list is refreshed.

表示动态数据集合，在添加、删除项目或刷新整个列表时提供通知。

class BrowserViewModel
{
    #region Properties

    public ObservableCollection<TreeViewModel> Status { get; private set; }
    public string Conditions { get; private set; }

    #endregion // Properties

    // i'd like to call this method when Status gets updated
    void updateConditions
    {
         /* Conditions = something */
    }

    public BrowserViewModel()
    {
        Status = new ObservableCollection<TreeViewModel>();
        Status.CollectionChanged += (e, v) => updateConditions();
    }
}

CollectionChanged will fire whenever an item is added/removed/changed. As far as I know, it will consider it "changed" when its reference changes or any of its properties are changed (which is notified through INotifyPropertyChanged)

每当添加/删除/更改项目时，CollectionChanged 都会触发。据我所知，当它的引用更改或其任何属性发生更改（通过 通知INotifyPropertyChanged）时，它会认为它“已更改”

Just checked it here: http://msdn.microsoft.com/en-us/library/ms653375.aspx

刚刚在这里检查：http: //msdn.microsoft.com/en-us/library/ms653375.aspx

ObservableCollection.CollectionChanged Event Occurs when an item is added, removed, changed, moved, or the entire list is refreshed.

ObservableCollection.CollectionChanged 事件在添加、删除、更改、移动项目或刷新整个列表时发生。

ObservableCollection<T>resides in the System.Collections.ObjectModelnamespace, in System.dllassembly.

ObservableCollection<T>驻留在System.Collections.ObjectModel命名空间中，在System.dll程序集中。