CODEWITHSUNDEEP
c#wpf
Zelid
Zelid

Reputation: 7195

Update current class property when any item in observable collection changes

I have a class

public class SomeModel : INotifyPropertyChanged {

  public ObservableCollection<SomeSubModel> SubModels {get; set;}

  public int Sum { get { return SubModels.Sum(x=> x.Count) }}

  private string _url;
  public string Url
  {
    get { return _url; }
    set
    {
        _url = value;
        OnPropertyChanged();
    }
  }

  public event PropertyChangedEventHandler PropertyChanged;

  [NotifyPropertyChangedInvocator]
  protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
  {
    var handler = PropertyChanged;
    if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
  }

}

public class SomeSubModel : INotifyPropertyChanged {

  private string _count;
  public string Count
  {
    get { return _count; }
    set
    {
        _count = value;
        OnPropertyChanged();
    }
  }

  public event PropertyChangedEventHandler PropertyChanged;

  [NotifyPropertyChangedInvocator]
  protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
  {
    var handler = PropertyChanged;
    if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
  }

}

I'm going to use binding to SomeSubModel.Sum in WPF UI.

The SomeSubModel.Count property is changed very frequently.

How to notify that SomeSubModel.Sum is changed when property SomeSubModel.Count from any item in SomeModel.SubModels observable collection is changed to reflect the actual SomeSubModel.Sum in WPF UI through the binding?

The main goal is to reflect in UI the actual Sum of all Count's of objects in observable collection.

Thank you!

Upvotes: 0

Views: 516

Answers (1)

Kenneth
Kenneth

Reputation: 28737

You should fire a notify property changed for the Sum property as well in that case:

private string _count;
public string Count
{
    get { return _count; }
    set
    {
        _count = value;
        OnPropertyChanged();
        var handler = PropertyChanged;
        if (handler != null) 
            handler(this, new PropertyChangedEventArgs("Sum"));
    }
}

Upvotes: 2

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