WPF DataGrid binding doesn't update

Question

Here's my DataGrid:

<DataGrid x:Name="MoonMining" 
          ItemsSource="{Binding MarketData.MoonMinerals, ElementName=window}">
    <DataGrid.DataContext>
        <local:MoonMineral/>
    </DataGrid.DataContext>
    <DataGrid.Columns>
        .. Yes i have columns and they are irrelevant to my question .
    </DataGrid.Columns>
</DataGrid>

MarketData is a class which contains most of my programs logic. MoonMinerals is defined in that class:

public class MarketData
{
   private ObservableCollection<MoonMineral> _moonMinerals = new ObservableCollection<MoonMineral>();

   public ObservableCollection<MoonMineral> MoonMinerals
   {
       get { return _moonMinerals; }
       set { _moonMinerals = value; }
   }
 }

And here's my MoonMineral class:

[NotifyPropertyChanged]
public class MoonMineral
{
    public MoonMineral()
        : this("Def", "Def")
    {
    }

    public MoonMineral(string name, string rarity)
    {
        Name = name;
        Rarity = rarity;
    }

    public string Name { get; set; }
    public double Price { get; set; }
    public double Volume { get; set; }
    public string Rarity { get; set; }
    public double TransportVolume { get; set; }
    public double TransportCosts { get; set; }
    public double GrossProfit { get; set; }
    public double NetProfit { get; set; }
}

As you can see, I'm using PostSharp to clear up my code, but when I manually implement INotifyPropertyChanged I have the same problem.

Now the problem is that my DataGrid doesn't update by itself, I have to manually call this in a method which modifies MoonMinerals:

var bindingExpression = MoonMining.GetBindingExpression(ItemsControl.ItemsSourceProperty);
if (bindingExpression != null)
    bindingExpression.UpdateTarget();

I know this isn't big of a deal, but I wanted to finally manage to bind data to ui entirely using xaml. All my previous attempts involved setting DataGrids ItemsSource property every time I updated the data.

Do you change MoonMinerals property and if yes will it raise PropertyChanged event like properties of MoonMineral? — dkozl
– dkozl, Commented Sep 1, 2014 at 20:05
i don't understand where MarketData is .. could you show the class . and why is your item source binding to ElementName=window — eran otzap
– eran otzap, Commented Sep 1, 2014 at 20:05
@dkozl I'm using PostSharp to do that for me, but yes, I've tried raising it manually also and it did not work. — Krzaku
– Krzaku, Commented Sep 1, 2014 at 20:07
I can see you do it for MoonMineral class but do you do it for class which exposes ObservableCollection<MoonMineral> MoonMinerals property, which in your case seems to be some window? — dkozl
– dkozl, Commented Sep 1, 2014 at 20:09

dkozl · Accepted Answer · 2014-09-01 20:27:19Z

4

To sum up comments you're implementing INotifyPropertyChanged interface for MoonMineral class and use ObservableCollection which will handle changes to the collection but there seems to be nothing in place to handle changes to MoonMinerals property

private ObservableCollection<MoonMineral> _moonMinerals = new ObservableCollection<MoonMineral>();

public ObservableCollection<MoonMineral> MoonMinerals
{
    get { return _moonMinerals; }
    set { _moonMinerals = value; }
}

You can either implement INotifyPropertyChanged interface in the class that exposes MoonMinerals property or change it to read-only and use only one instance of _moonMinerals and simply clear it and add/remove items

private readonly ObservableCollection<MoonMineral> _moonMinerals = new ObservableCollection<MoonMineral>();

public ObservableCollection<MoonMineral> MoonMinerals
{
    get { return _moonMinerals; }
}

Also, as a side note, you don't need

<DataGrid.DataContext>
    <local:MoonMineral/>
</DataGrid.DataContext>

as this will set DataContext of the DataGrid to new instance of MoonMineral. It works in your case as you change binding context of ItemsSource using ElementName so DataContext is not used in your case.

answered Sep 1, 2014 at 20:27

dkozl

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1 Comment

Krzaku Over a year ago

Thanks, implementing INotifyPropertyChanged on the class that exposes MoonMinerals worked. About that side note though, I might still need it, I get a notification "cannot resolve symbol" when I bind a Setters value on one of the columns if DataContext is not set. The Setter still works even with that notification so I'm not sure what's up.

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