Monitoring other classes with one class

Question

I have one class named DataClass. This Class is responsible to saving information in database, and In this class there are some methods for saving and reading from database, Except this class I have other classes called HTMLEditor, QueryBuilder , EmailSending, InforDetails. I need to listen to other classes by my data class , any time their information are changed then my Dataclass would be notified to save these information. I know there is one design pattern is called observer design pattern , with this design pattern, other classes(observers) are listening to one class(subject),any time the status of subject is changed then other observers are notified.

What should I do for this problem? Is there any design pattern for this situation?

score 2 · Accepted Answer · answered Nov 21 '12 at 01:21

2

I think the interface you seek if INotifyPropertyChanged.

Microsoft Documentation: INotifyPropertyChanged

The implementation is very simple.

In every property set you do:

public bool MyProperty
{
    get { return myField; }

    set
    {
        if (myField != value)
        {
            myField= value;
            NotifyPropertyChanged();
        }
    }
}

And the method and events:

public event PropertyChangedEventHandler PropertyChanged;

private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
{
    if (PropertyChanged != null)
    {
        PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
}

Every observer only need to register to that event and they get a feedback when a property changed and which one did.

As extra, some control like PropertyGrid automatically register themselves when you feed them an object that implement that interface.

answered Nov 21 '12 at 01:21

LightStriker

19,738
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Thanks, Your solution works inside a class, How can I extend it to other classes? – Houshang.Karami Nov 21 '12 at 01:26
@PersianGolf: What do you mean "other classes"? Other classes as in classes that you cannot modify? – LightStriker Nov 21 '12 at 01:28
In other classes If some property change, Then my DataClass should be notified to do some action, Like as saving. – Houshang.Karami Nov 21 '12 at 01:35
@PersianGolf: So implement that interface in all the classes you want to monitor? – LightStriker Nov 21 '12 at 01:40
This solution works for internally notification(in each class), I need notification between classes. – Houshang.Karami Nov 21 '12 at 01:57
@PersianGolf: Registre a delegate in the event! – LightStriker Nov 21 '12 at 05:21

score 1 · Answer 2 · edited May 23 '17 at 12:27

1

The INotifyPropertyChanged interface could be what you're after:

See here: http://msdn.microsoft.com/en-us/library/system.componentmodel.inotifypropertychanged.aspx

You basically subscribe to an event within your other classes and those classes raise the event when a property changes.

Also, this SO question has an answer that is quite cool: Automatically INotifyPropertyChanged

edited May 23 '17 at 12:27

Community

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1

answered Nov 21 '12 at 01:18

Simon Whitehead

63,300
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Monitoring other classes with one class

2 Answers2