WF,WPF,Silverlight的DependencyProperty 附加属性

注意,是DependencyProperty 附加属性,而不是绑定属性

例子: http://files.cnblogs.com/foundation/Projects.rar

首先看一个假设,

在不修改一个类的前提下,如何扩展一个类的成员(继承也不可以)

这在传统的OO设计中是无法完成的,但在NET3.0(C#3.0,VB.NET9.0)中提供了扩展方法开实现这一功能

看下例:

场景:我经常要用得到数字除2的结果,如何方便的实现

class Program

{

static void Main(string[] args)

{

double v1 = 123;

double p1 = v1.zzzzz();

System.Console.WriteLine(p1);

//--

double p2=(1234567890.123).zzzzz();

System.Console.WriteLine(p2);

}

static class myExtension

{

public static double zzzzz(this double d)

{

return d/2 ;

}

这就是扩展方法,在不修改的结构的情况下,为[ double ]添加了[zzzzz]这个方法

linq 用的就是这种方式

方法可以这样做,那属性哪?

升级一下需求,我想一个对象在一个环境中自动多出某几个属性,在另外一个环境中又自动多出另外几个属性

如何做,

先看一下Silverlight

场景:提供一个容器,容器分两排,放入容器内的件意控件都可设置附加属性[myTag]的属性,[myTag]属性设为[a]的在左边,设为[b]的在右边

容器

public class wxdPanel : StackPanel

{

StackPanel p1 = new StackPanel();

StackPanel p2 = new StackPanel();

public wxdPanel()

: base()

{

p1.Width = 200;

p2.Width = 200;

p1.Background = new System.Windows.Media.SolidColorBrush(new Color() { R = 0, G=255, B=0 , A=255});

p2.Background = new System.Windows.Media.SolidColorBrush(new Color() { R = 0, G = 0, B = 255, A = 255 });

this.Orientation = Orientation.Horizontal;

this.Children.Add(p1);

this.Children.Add(p2);

this.Loaded += new RoutedEventHandler(wxdPanel_Loaded);

}

List<FrameworkElement> list = new List<FrameworkElement>();

void wxdPanel_Loaded(object sender, RoutedEventArgs e)

{

foreach (var p in this.Children)

{

if (p is StackPanel)

{

}

else

{

list.Add((FrameworkElement)p);

}

foreach (var v in list)

{

this.Children.Remove(v);

if (wxdPanel.GetmyTag(v) == "a")

{

p1.Children.Add(v);

}

if (wxdPanel.GetmyTag(v) == "b")

{

p2.Children.Add(v);

}

public static string GetmyTag(DependencyObject obj)

{

return (string )obj.GetValue(myTagProperty);

}

public static void SetmyTag(DependencyObject obj, string value)

{

obj.SetValue(myTagProperty, value);

}

public static readonly DependencyProperty myTagProperty = DependencyProperty.RegisterAttached("myTag", typeof(string ), typeof(wxdPanel),new PropertyMetadata(""));

}

使用

<UserControl x:Class="SilverlightApplication1.Page"

xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

Width="400" Height="300" xmlns:mytype="clr-namespace:SilverlightApplication1">

<mytype:wxdPanel >

</mytype:wxdPanel>

</UserControl>

效果

WPF的实现

与Silverlight 相同

再看一下WF的实现

场景:提供一个容器,放入容器内的件意Activity会多出一个明为[myTag]的属性,[myTag]属性设为[a]的执行,设为[b]的不执行

先创建这个容器Activity

[Designer(typeof(myDesigner), typeof(IDesigner))]

public partial class myContainer : System.Workflow.ComponentModel.CompositeActivity

{

//-

public static string GetmyTag(object obj)

{

DependencyObject dObject = obj as DependencyObject;

object value = dObject.GetValue(myTagProperty);

return value.ToString();

}

public static void SetmyTag(object obj, string value)

{

DependencyObject dObject = obj as DependencyObject;

dObject.SetValue(myTagProperty, value);

}

public static readonly DependencyProperty myTagProperty = DependencyProperty.RegisterAttached("myTag", typeof(string), typeof(myContainer), new PropertyMetadata(""));

public static string GetleftValue(object obj)

{

DependencyObject dObject = obj as DependencyObject;

object value = dObject.GetValue(leftValueProperty);

return value.ToString();

}

public static void SetleftValue(object obj, object value)

{

DependencyObject dObject = obj as DependencyObject;

dObject.SetValue(leftValueProperty, value);

}

public static readonly DependencyProperty leftValueProperty = DependencyProperty.RegisterAttached("leftValue", typeof(string), typeof(myContainer), new PropertyMetadata(""));

int n = 0;

protected override ActivityExecutionStatus Execute(ActivityExecutionContext executionContext)

{

n = this.EnabledActivities.Count;

if (n == 0)

{

return ActivityExecutionStatus.Closed;

}

foreach (Activity activity in this.EnabledActivities)

{

n = n - 1;

string l = myContainer.GetmyTag(activity);

if (l == "a")

{

activity.Closed += new EventHandler<ActivityExecutionStatusChangedEventArgs>(activity_Closed);

executionContext.ExecuteActivity(activity);

}

return ActivityExecutionStatus.Executing;

}

void activity_Closed(object sender, ActivityExecutionStatusChangedEventArgs e)

{

ActivityExecutionContext executionContext = sender as ActivityExecutionContext;

if (n == 0)

{

executionContext.CloseActivity();

}

[ProvideProperty("myTag", typeof(Activity))]

public class myExtenderProvider : IExtenderProvider

{

public bool CanExtend(object extendee)

{

return (((extendee != this) && (extendee is Activity)) && (((Activity)extendee).Parent is myContainer));

}

//-

public string GetmyTag(Activity activity)

{

if (activity.Parent is myContainer)

{

return activity.GetValue(myContainer.myTagProperty).ToString();

}

return null;

}

public void SetmyTag(Activity activity, string value)

{

if (activity.Parent is myContainer)

{

activity.SetValue(myContainer.myTagProperty, value);

}

public class myDesigner : SequenceDesigner

{

protected override void Initialize(Activity activity)

{

base.Initialize(activity);

IExtenderListService service = (IExtenderListService)base.GetService(typeof(IExtenderListService));

if (service != null)

{

bool tag = false;

foreach (IExtenderProvider provider in service.GetExtenderProviders())

{

if (provider.GetType() == typeof(myExtenderProvider))

{

tag = true;

}

if (!tag)

{

IExtenderProviderService tempService = (IExtenderProviderService)base.GetService(typeof(IExtenderProviderService));

if (tempService != null)

{

tempService.AddExtenderProvider(new myExtenderProvider());

}

然后设计工作流

运行结果