Routed events and dependency properties .NET wrapper confusion

问题

I'm new to WPF and have a confusion about wrapping syntax of routed events and dependency properties I've seen on many sources that routed events and dependency properties are wrapped like this

// Routed Event
public event RoutedEventHandler Click
{
 add
 {
  base.AddHandler(ButtonBase.ClickEvent, value);
 }
 remove
 {
  base.RemoveHandler(ButtonBase.ClickEvent, value);
 }
}

// Dependency Property
public Thickness Margin
{
 set { SetValue(MarginProperty, value); }
 get { return (Thickness)GetValue(MarginProperty); }
}

I have never seen add / remove / set / get sort of keywords in C#. Are these are part of C# language as Keywords and i never experienced or worked with them because i didn't worked in C# as pro i'm a C++ programmer? If not keywords then how they are handled by compiler if they are not part of C# and how they are working

回答1:

I'm gonna try to sum it up for you:

Dependency property:

public int MyProperty
{
    get { return (int)GetValue(MyPropertyProperty); }
    set { SetValue(MyPropertyProperty, value); }
}

// Using a DependencyProperty as the backing store for MyProperty.  This enables animation, styling, binding, etc...
public static readonly DependencyProperty MyPropertyProperty =
    DependencyProperty.Register("MyProperty", typeof(int), typeof(MyClass), new UIPropertyMetadata(MyDefaultValue));

That's the full syntax, you don't have to memorize it, just use the "propdp" snippet in Visual Studio.
The "get" must return a value of the type it refers to (in my example, int). Whenever you call

int MyVar = MyProperty;

The code inside "get" is evaluated.
The set has a similar mechanism, only you have another keyword: "value" which will be the value you assign to MyVariable:

MyProperty = 1;

Will call the "set" of MyProperty and "value" will be "1".

Now for the RoutedEvents:

In C# (as in C++, correct me if i'm wrong), to subscribe to an event, you do

MyProperty.MyEvent += MyEventHandler;

That will call the "add" --> you're adding a handler to the stack. Now since it is not automatically garbage-collected, and we want to avoid memory leaks, we do:

MyProperty.MyEvent -= MyEventHandler;

So that our object can be safely disposed of when we don't need it anymore. That's when the "remove" expression is evaluated.

Those mechanism allow you to do multiple things on a single "get", a widely used example in WPF would be:

private int m_MyProperty;
public int MyProperty
{
   get
   {
      return m_MyProperty;
   }
   set
   {
      if(m_MyProperty != value)
      {
         m_MyProperty = value;
         RaisePropertyChanged("MyProperty");
       }
    }
}

Which, in a ViewModel that implements INotifyPropertyChanged, will notify the bindings in your View that the property has changed and need to be retrieved again (so they will call the "get")

来源：https://stackoverflow.com/questions/7538693/routed-events-and-dependency-properties-net-wrapper-confusion

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wpf

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dependency-properties

routed-events