WPF GridView Not Updating On Observable Collection Change

I have a Telerik RadGridView Bound to ObservableCollection of defined type.. On Updating the value of a particular property in that type, the corresponding Observable collection is getting updated but not the RadGridView..

Below is the XAML:

<ComboBox Grid.Column="4" Width="100" Margin="4" ItemsSource="{Binding Path=ResultUnits, Mode=OneTime}" SelectedValue="{Binding Path=ResultUnit}"/>

<telerik:RadGridView ItemsSource="{Binding Path=Results, Mode=TwoWay}" FooterRowStyle="{StaticResource GridViewFooterStyle}" Width="{Binding RelativeSource={RelativeSource AncestorType= ScrollViewer}, Path=ActualWidth}" ColumnWidth开发者_如何学Go="*" RowIndicatorVisibility="Collapsed" EditTriggers="None" IsFilteringAllowed="False" AutoGenerateColumns="False" AllowDrop="False" CanUserFreezeColumns="False" CanUserReorderColumns="False" CanUserDeleteRows="False" CanUserInsertRows="False" ShowGroupPanel="False" ShowColumnFooters="True">
 <telerik:RadGridView.Columns>
  <telerik:GridViewDataColumn Header="Quantity" DataMemberBinding="{Binding Path=Quantity}"/>
  </telerik:RadGridView.Columns>
</telerik:RadGridView>

Below is the View Model Code:

public class ViewModel {

    private const decimal PoundsToKilograms = 0.45359237M;

    private const decimal GramstoPound = 0.00220462262M;

    private ObservableCollection<Result> results;

    public EnvironmentalSummaryViewModel() {
        this.results= new ObservableCollection<Result>();
    }

    public ObservableCollection<Result> Results{
        get {
            return this.results;
        }

        set {
            this.results = value;
        }
    }

  public string ResultUnit {
        get {
            return this.resultUnit;
        }

        set {
            if (this.resultUnit != value) {
                this.resultUnit = value;
                this.UpdateGridViewValuesOnResultUnitChanged();
            }
        }
    }

   private void UpdateGridViewValuesOnResultUnitChanged() {
        bool isEnglish = this.resultUnit == this.resultUnits[0];
        this.results.ToList().ForEach(result => {
            decimal weight = isEnglish ? result.Weight * GramstoPound * 1000 : environmental.Weight * PoundsToKilograms;
            result.Weight = Math.Round(weight, 2);
        });

        ((IHaveOnPropertyChangedMethod) this).OnPropertyChanged("Results");
    }
}

Object Class:

public class Result{
   public decimal Weight { get; set; }
}

Each item within the Observable Collection must have a way to signal to WPF and therefore the control that it is updating so that the Quantity Value can be updated. The Observable Collection update is occuring because that collection contains in built change notification for its collection but not its individual items. As others have said implement INotifyPropertyChanged on Result and it should work.

public class Result : INotifyPropertyChanged
{

    #region INotifyPropertyChanged Members

    public event PropertyChangedEventHandler PropertyChanged;

    protected void Notify(string propName)
    {
        if (this.PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propName));
        }
    }
    #endregion


    private decimal _weight;

    public decimal Weight
    {
        get { return _weight; }
        set { 

            this._weight = value;
            Notify("Weight");
        }
    }
}

As Erno said your Result class needs to implement INotifyPropertyChanged and you need to call OnPropertyChanged for the Weight property.

Also, your ViewModel should also implement INotifyPropertyChanged so you can avoid the casting to IHaveOnPropertyChangedMethod (that naming is pretty bad btw) that you have in your code. I would suggest having a ViewModelBase : INotifyPropertyChanged class that all your ViewModels inherit from. If you don't want to write one yourself there are plenty of MVVM frameworks out there that have this built in.

If the update that you are making is an update to the Weight property of a Result Object then this might be caused by the fact that the Result class is not inmplementing INotifyPropertyChanged.

ICollectionChanged (and thus ObservableCollection too) only notifies changes to the collection (adding and removing items).