[英]Binding to a dictionary in Silverlight with INotifyPropertyChanged
在Silverlight中,我无法让INotifyPropertyChanged在绑定到字典时像我想要的那样工作。 在下面的示例中,页面可以正常绑定到字典,但是当我更改其中一个文本框的内容时,不会调用CustomProperties属性setter。 CustomProperties属性设置器仅在设置CustomProperties时调用,而不是在设置其中的值时调用。 我试图对字典值进行一些验证,所以我希望在字典中的每个值都改变时运行一些代码。 我能在这做什么吗?
C#
public partial class MainPage : UserControl
{
public MainPage()
{
InitializeComponent();
MyEntity ent = new MyEntity();
ent.CustomProperties.Add("Title", "Mr");
ent.CustomProperties.Add("FirstName", "John");
ent.CustomProperties.Add("Name", "Smith");
this.DataContext = ent;
}
}
public class MyEntity : INotifyPropertyChanged
{
public event PropertyChangedEventHandler System.ComponentModel.INotifyPropertyChanged.PropertyChanged;
public delegate void PropertyChangedEventHandler(object sender, System.ComponentModel.PropertyChangedEventArgs e);
private Dictionary<string, object> _customProps;
public Dictionary<string, object> CustomProperties {
get {
if (_customProps == null) {
_customProps = new Dictionary<string, object>();
}
return _customProps;
}
set {
_customProps = value;
if (PropertyChanged != null) {
PropertyChanged(this, new PropertyChangedEventArgs("CustomProperties"));
}
}
}
}
VB
Partial Public Class MainPage
Inherits UserControl
Public Sub New()
InitializeComponent()
Dim ent As New MyEntity
ent.CustomProperties.Add("Title", "Mr")
ent.CustomProperties.Add("FirstName", "John")
ent.CustomProperties.Add("Name", "Smith")
Me.DataContext = ent
End Sub
End Class
Public Class MyEntity
Implements INotifyPropertyChanged
Public Event PropertyChanged(ByVal sender As Object, ByVal e As System.ComponentModel.PropertyChangedEventArgs) Implements System.ComponentModel.INotifyPropertyChanged.PropertyChanged
Private _customProps As Dictionary(Of String, Object)
Public Property CustomProperties As Dictionary(Of String, Object)
Get
If _customProps Is Nothing Then
_customProps = New Dictionary(Of String, Object)
End If
Return _customProps
End Get
Set(ByVal value As Dictionary(Of String, Object))
_customProps = value
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs("CustomProperties"))
End Set
End Property
End Class
XAML
<TextBox Height="23" Name="TextBox1" Text="{Binding Path=CustomProperties[Title], Mode=TwoWay}" />
<TextBox Height="23" Name="TextBox2" Text="{Binding Path=CustomProperties[FirstName], Mode=TwoWay}" />
<TextBox Height="23" Name="TextBox3" Text="{Binding Path=CustomProperties[Name], Mode=TwoWay}" />
这是一个(有点过于简化)的解决方案。
public class MyEntity : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private readonly Dictionary<string, object> _customProps = new Dictionary<string, object>();
public void AddCustomProperty(string key, object value)
{
_customProps.Add(key, value);
}
public object this[string key]
{
get { return _customProps[key]; }
set
{
// The validation code of which you speak here.
_customProps[key] = value;
NotifyPropertyChanged("Item[" + key "]");
}
}
private void NotifyPropertyChanged(string name)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(name));
}
}
主页:-
public MainPage()
{
InitializeComponent();
MyEntity ent = new MyEntity();
ent.AddCustomProperty("Title", "Mr");
ent.AddCustomProperty("FirstName", "John");
ent.AddCustomProperty("Name", "Smith");
this.DataContext = ent;
}
MainPage Xaml: -
<TextBox Height="23" Name="TextBox1" Text="{Binding [Title], Mode=TwoWay}" />
<TextBox Height="23" Name="TextBox2" Text="{Binding [FirstName], Mode=TwoWay}" />
<TextBox Height="23" Name="TextBox3" Text="{Binding [Name], Mode=TwoWay}" />
对于您的问题,重要的是您的代码涉及将属性值分配到字典中。 最初你的代码暴露了Dictionary
,所有的赋值工作都经过了框架组件代码。 在此版本中, MyEntity
有一个字符串索引器,其中直接分配自定义属性,并使Dictionary
成为私有。
请注意, INotifyPropertyChanged
的实现对于回答您的具体问题并非绝对必要,但我怀疑您将需要它。 例如,如果您将新值重新分配给自定义属性,则需要通知UI。
除了INotifyPropertyChanged接口之外,集合还需要实现INotifyCollectionChanged 接口以支持数据绑定。 ObservableCollection类为类似List的集合实现它们,但我相信.NET Framework中没有类似字典的集合来执行此操作。 您可能必须自己实施它。
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