Hook Event for All Property Set?

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lucius - 09 Jul 2007 15:32 GMT

Can I have an example of wiring up an Event (handler) that can be
fired no matter what property Set accessor is touched? I have a lot of
get/sets on public properties and I would like to create something in
the class constructor that would be automatically called whenever
anything was Set.

Thanks.

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Steven Cheng[MSFT] - 10 Jul 2007 07:05 GMT

Hi Lucius,

Regarding on the central property setting event hooking request, based on
my understanding, so far we have to manually add some code to monitor all
the properties's get/set operations. This is because there is no built-in
pipeline or channel chain (for property setting/getting) for normal .NET
framework classes. If you do want to make your classes have such ability,
you can consider the following approaches:

** Add a event handler for your class that will react on propery get or
set. And in each of your class property's getter or setter, manually add
code to raise that event (and invoke the eventhandler).

** Or you can always use a central method or property to get/set other
properties(using reflection code in it). Thus, you can put your event
hooking code in that central place:

http://www.devhood.com/tutorials/tutorial_details.aspx?tutorial_id=646

BTW, there is another AOP like approach for you to define a proxy class
which will router any method calls to the backend real class instance.
However, using this maybe a bit to expensive for your scenario here. Just
mention it for your refererence:

#Aspect Oriented Programming using .NET - AOP in C#
http://www.developerfusion.co.uk/show/5307/3/

http://www.ayende.com/Blog/archive/2007/07/02/7-Approaches-for-AOP-in-.Net.a
spx

Hope this helps some.

Sincerely,

Steven Cheng

Microsoft MSDN Online Support Lead

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Reply to this Message

lucius - 10 Jul 2007 16:57 GMT

Yes, you understand my issue. Can you please code a sample that does

"

>** Add a event handler for your class that will react on propery get or
>set. And in each of your class property's getter or setter, manually add
>code to raise that event (and invoke the eventhandler).

"
Please?

Thanks.

>Hi Lucius,
>
[quoted text clipped - 56 lines]
>
>This posting is provided "AS IS" with no warranties, and confers no rights.

Reply to this Message

Steven Cheng[MSFT] - 11 Jul 2007 05:08 GMT

Hi lucius,

for the first approach, as Philip has also mentioned, here is a simple
implementation:

======================================
public delegate void PropertyChangeEventHandler(string propname, object
propvalue);

public class EventClass
{
private string _prop1;
private int _prop2;

public event PropertyChangeEventHandler PropertyChanged;

public EventClass()
{

}

public string Property1
{
get { return _prop1; }
set {
_prop1 = value;
if (PropertyChanged)
{
PropertyChanged("Property1", value);
}
}
}

public int Property2
{
get { return _prop2; }
set {
_prop2 = value;
if (PropertyChanged)
{
PropertyChanged("Property2", value);
}
}
}

}
=======================================

For the other global property approach, the article I refered has well
demonstrated the usage of global property(through reflection).

Sincerely,

Steven Cheng

Microsoft MSDN Online Support Lead

This posting is provided "AS IS" with no warranties, and confers no rights.

Reply to this Message

Steven Cheng[MSFT] - 13 Jul 2007 08:13 GMT

Hi Lucius,

Does the further info also help some? If there is anything else need help,
please don't hesitate to post here.

Sincerely,

Steven Cheng

Microsoft MSDN Online Support Lead

This posting is provided "AS IS" with no warranties, and confers no rights.

Reply to this Message

PhilipDaniels@foo.com - 10 Jul 2007 19:37 GMT

>Can I have an example of wiring up an Event (handler) that can be
>fired no matter what property Set accessor is touched? I have a lot of
[quoted text clipped - 3 lines]
>
>Thanks.

I don't think (never say never...) it can be done "automagically" -
instead, you will have to add some code into each setter to raise the
event. BTW, the INotifyPropertyChanged interface exists for this
purpose. There's an example in the help.

--
Philip Daniels

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Hook Event for All Property Set?

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