MVVM: Raise PropertyChanged event for a DataContract class members

Question

I want to raise PropertyChanged event for a model with DataContract. Initially I did this

[DataContract]
public partial class User : INotifyPropertyChanged
{
    [DataMember(Name="username")]
    public string Username
    {
        get
        {
            return this.Username;
        }
        set
        {
            this.Username = value;
            RaisePropertyChanged("Username");
        }
    }
}

which gave StackOverflow Exception beacause of Infinite Recursion.

So the solution I come up with is

[DataContract]
public partial class User : INotifyPropertyChanged
{
    private string _Username { get; set; }
    [DataMember(Name="username")]
    public string Username
    {
        get
        {
            return this._Username;
        }
        set
        {
            this._Username = value;
            RaisePropertyChanged("Username");
        }
    }
}

Although this reflects the Username value to the control binding to "Username", this doesn't look the best way to me. Something is wrong. Also my model has approx 30-40 fields. Is this the right approach or can someone please suggest me a better way.

Thanks

That is generally the right way. Yes, there are slightly fancier ways of raising notifications, but what you've done will work fine for now. You can get rid of the `this.` in front of the private member assignment. http://stackoverflow.com/a/13720780/109702 — slugster, Aug 21 '14 at 12:42
There's no need for `_Username` to be a property; that should be a field. — Marc Gravell, Aug 21 '14 at 12:45

score 3 · Accepted Answer · answered Aug 21 '14 at 12:42

3

I'd be so tempted to use caller-member-name here (if it is in your target framework):

private string _username;
[DataMember(Name="username")]
public string Username
{
    get { return _username; }
    set { SetField(ref _username, value); }
}

private void SetField<T>(ref T field, T value,
    [CallerMemberName] string memberName = null)
{
    if(!EqualityComparer<T>.Default.Equals(field,value))
    {
        field = value;
        RaisePropertyChanged(memberName);
    }
}

If caller-member-name isn't supported:

[DataMember(Name="username")]
public string Username
{
    get { return this._Username; }
    set { SetField(ref _Username, value, "Username"); }
}

answered Aug 21 '14 at 12:42

Marc Gravell

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Thanks. [CallerMemberName] isn't supported in windows-phone. – pratpor Aug 21 '14 at 13:01
2

@PratPor that actually depends on what compiler you're using; since it is **entirely** a compiler feature (not a framework feature), you can actually declare the attribute yourself (in the right namespace etc) - if you are using an up-to-date compiler, *it will work* – Marc Gravell Aug 21 '14 at 13:06

score 2 · Answer 2 · answered Aug 21 '14 at 12:41

[DataContract]
public partial class User : INotifyPropertyChanged
{
    private string _Username;

    [DataMember(Name="username")]
    public string Username
    {
        get
        {
            return this._Username;
        }
        set
        {
            if(this._Username != value)
            {
                this._Username = value;
                RaisePropertyChanged("Username");
            }
        }
    }
}

MVVM: Raise PropertyChanged event for a DataContract class members

2 Answers2