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List vs ObservableCollection vs INotifyPropertyChanged in Silverlight

By , , 21 Sep 2009
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Introduction

This article describes the basic understanding between List, ObservableCollection and INotifyPropertyChanged.

Difference between List<T>, ObservableCollection<T> and INotifyPropertyChanged

List<T>

It represents a strongly typed list of objects that can be accessed by index. It provides methods to search, sort, and manipulate lists. The List<T> class is the generic equivalent of the ArrayList class. It implements the IList<T> generic interface using an array whose size is dynamically increased as required.

Drawbacks

In ASP.NET, we simply use DataSource and DataBind() to bind the data, but in Silverlight it is slightly different. Databinding in ASP.NET is done in a stateless way - once that binding operation is completed, it's a done deal and if you want to change anything, you have to manipulate the underlying controls that were created as a result of the data binding, or else change the underlying data objects and call DataBind() again. That’s what we are used to – but it’s not a good practice.

listgrid.JPG

In the sample application, the values in the list are added, removed and changed during runtime in the code behind. The changes in the list will not be updated to the UI (Datagrid).

ObservableCollection<T>

ObservableCollection is a generic dynamic data collection that provides notifications (using an interface "INotifyCollectionChanged") when items get added, removed, or when the whole collection is refreshed.

Note: WCF service proxy class in Silverlight will use this type of collection by default.

observablecollection.JPG

Drawbacks

It does not provide any notifications when any property in the collection is changed.

observablecollectiongrid.JPG

In the sample application, the values in the observable collection are added, removed and changed during runtime in the code behind. The operations (adding and removing an item) in the observable collection will be updated to the UI (Datagrid). But any change in the existing item will not be updated to the UI.

INotifyPropertyChanged

INotifyPropertyChanged is not a collection, it’s an interface used in the data object classes to provide PropertyChanged notification to clients when any property value gets changed. This will allow you to raise PropertyChanged event whenever the state of the object changes (Added, Removed, and Modified) to the point where you want to notify the underlying collection or container that the state has changed.

inotifypropertychanged.JPG

inotifypropertychangedgrid.JPG

INotifyPropertyChanged is compatible on all type of collections like List<T>, ObservableCollection<T>, etc. The code snippet which uses INotifyPropertyChanged is shown below:

public class UserNPC:INotifyPropertyChanged
{
    private string name;
    public string Name { 
        get { return name; } 
        set { name = value; onPropertyChanged(this, "Name"); } 
    }
    public int grade;
    public int Grade { 
        get { return grade; } 
        set { grade = value; onPropertyChanged(this, "Grade"); } 
    }

    // Declare the PropertyChanged event
    public event PropertyChangedEventHandler PropertyChanged;

    // OnPropertyChanged will raise the PropertyChanged event passing the
    // source property that is being updated.
    private void onPropertyChanged(object sender, string propertyName)
    {
        if (this.PropertyChanged != null)
        {
            PropertyChanged(sender, new PropertyChangedEventArgs(propertyName));
        }
    }
}

In the above code snippet, whenever a value is set to a property, the method “onPropertyChanged” will be called which in turn raises the PropertyChanged event.

History

  • 22nd September, 2009: Initial post

License

This article, along with any associated source code and files, is licensed under The Creative Commons Attribution-ShareAlike 2.5 License

About the Authors

BalaG Ganesan
Technical Lead Infosys
India India
Working as a Technology Lead in Infosys at Chennai, India.

Venkatesan Jagadisan
Software Developer iSOFT
India India
Working as a Software Engineer in iSOFT at Chennai, India.

Comments and Discussions

 
GeneralMy vote of 4 PinmemberRajibdotnet053-Apr-14 7:00 
GeneralMy vote of 5 PinmemberURVISH_SUTHAR124-Dec-13 3:05 
QuestionGreat! PinmemberZia ur Rahman12-Dec-13 4:36 
GeneralMy vote of 5 PinmemberMember 98742804-Sep-13 21:47 
QuestionSuper PinmemberMember 1005388729-May-13 1:05 
QuestionThanks PinmemberMember 842326426-May-13 20:50 
GeneralMy vote of 5 PinmemberSavalia Manoj M17-Apr-13 2:23 
QuestionExcellent article, BUT PinmemberAslesh22-Jan-13 10:54 
GeneralMy vote of 5 Pinmemberhandachetan13-Jan-13 15:44 
GeneralMy vote of 4 PinmemberShah7308-Dec-12 23:34 
GeneralMy vote of 5 PinmemberRajesh Varma Buddaraju31-Oct-12 8:09 
GeneralMy vote of 5 PinmemberDellai Houssem23-Oct-12 7:42 
Questionexcellent Pinmemberbensonissac24-Sep-12 1:04 
GeneralMy vote of 5 PinmemberFarhan Ghumra24-Aug-12 0:53 
GeneralGood Article Pinmemberakhilesh saini19-Jul-12 5:43 
QuestionVote of 4 Pinmembersam344016-Jul-12 6:24 
GeneralMy vote of 4 Pinmembergovardhanpagidi29-Apr-12 20:26 
GeneralMy vote of 5 Pinmemberpiapp24-Apr-12 0:14 
GeneralGreat PinmemberMember 371070318-Apr-12 1:51 
QuestionIt's very good article. PinmemberAshokReddyProjects19-Jan-12 1:23 
GeneralMy vote of 5 Pinmemberm@dhu27-Dec-11 2:51 
QuestionExcellent Contrast PinmemberMember 15408993-Nov-11 7:00 
QuestionNice article PinmemberSaru.cool5-Sep-11 21:04 
GeneralGreat explanation: Vote of 5 PinmemberJaved Akhtar Ansari16-Aug-11 20:27 
QuestionCorrections... PinmemberMember 477740513-Jul-11 23:56 
Hello Actually Inotify only use to update the UI with changed values it is not use to add/Remove, it you want to use add/remove(for this you need to implement ObservableCollection) and Modify you need to implement INotify with Observable Collecions. Smile | :)

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