WPF DataContext does not refresh the DataGrid using MVVM model

Question

Project Overview

I have a view which binds to a viewmodel containing 2 ObserverableCollection. The viewmodel constructor populates the first ObserverableCollection and the view datacontext is collected to bind to it through a public property called Sites.

Later the 2ed ObserverableCollection is populated in the LoadOrders method and the public property LoadFraudResults is updated for binding it with datacontext.

I am using WCF to pull the data from the database and its getting pulled very nicely.

VIEWMODEL SOURCE

class ManageFraudOrderViewModel:ViewModelBase 
{
    #region Fields        
    private readonly ICollectionView collectionViewSites;
private readonly ICollectionView collectionView;
    private ObservableCollection<GeneralAdminService.Website> _sites;
    private ObservableCollection<FraudService.OrderQueue> _LoadFraudResults;

    #endregion 

    #region Properties
    public ObservableCollection<GeneralAdminService.Website> Sites 
    {
        get { return this._sites; }
    }
    public ObservableCollection<FraudService.OrderQueue> LoadFraudResults 
    {
        get { return this._LoadFraudResults;}
    }
    #endregion

    public ManageFraudOrderViewModel()
    {
        //Get values from wfc service model
        GeneralAdminService.GeneralAdminServiceClient generalAdminServiceClient = new GeneralAdminServiceClient();
        GeneralAdminService.Website[] websites = generalAdminServiceClient.GetWebsites();
        //Get values from wfc service model            

        if (websites.Length > 0)
        {
            _sites = new ObservableCollection<Wqn.Administration.UI.GeneralAdminService.Website>();
            foreach (GeneralAdminService.Website website in websites)
            {
                _sites.Add((Wqn.Administration.UI.GeneralAdminService.Website)website);
            }

 this.collectionViewSites= CollectionViewSource.GetDefaultView(this._sites);
        }
        generalAdminServiceClient.Close();
    }

    public void LoadOrders(Wqn.Administration.UI.FraudService.Website website)
    {
        //Get values from wfc service model            
        FraudServiceClient fraudServiceClient = new FraudServiceClient();
        FraudService.OrderQueue[] OrderQueue = fraudServiceClient.GetFraudOrders(website);
        //Get values from wfc service model            

        if (OrderQueue.Length > 0)
        {
            _LoadFraudResults = new ObservableCollection<Wqn.Administration.UI.FraudService.OrderQueue>();
            foreach (FraudService.OrderQueue orderQueue in OrderQueue)
            {
                _LoadFraudResults.Add(orderQueue);
            }
        }

    this.collectionViewSites= CollectionViewSource.GetDefaultView(this._LoadFraudResults);
        fraudServiceClient.Close();
    }

}

---

VIEW SOURCE

public partial class OrderQueueControl : UserControl {

    private ManageFraudOrderViewModel manageFraudOrderViewModel ;
    private OrderQueue orderQueue;
    private ButtonAction ButtonAction;
    private DispatcherTimer dispatcherTimer;

    public OrderQueueControl()
    {

            LoadOrderQueueForm();
    }

    #region LoadOrderQueueForm
    private void LoadOrderQueueForm()
    {    
    //for binding the first observablecollection
        manageFraudOrderViewModel = new ManageFraudOrderViewModel();
        this.DataContext = manageFraudOrderViewModel;          
    }
    #endregion

    private void cmbWebsite_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        BindItemsSource();
    }

    #region BindItemsSource
    private void BindItemsSource()
    {
        using (OverrideCursor cursor = new OverrideCursor(Cursors.Wait))
        {

            if (!string.IsNullOrEmpty(Convert.ToString(cmbWebsite.SelectedItem)))
            {
                    Wqn.Administration.UI.FraudService.Website website = (Wqn.Administration.UI.FraudService.Website)Enum.Parse(typeof(Wqn.Administration.UI.FraudService.Website),cmbWebsite.SelectedItem.ToString());

  //for binding the second observablecollection*******
                    manageFraudOrderViewModel.LoadOrders(website);
                    this.DataContext = manageFraudOrderViewModel;
  //for binding the second observablecollection*******
            }            
        }
    }
    #endregion

}

XAML

ComboBox x:Name="cmbWebsite" ItemsSource="{Binding Sites}" Margin="5" Width="100" Height="25" SelectionChanged="cmbWebsite_SelectionChanged"

DataGrid ItemsSource ={Binding Path = LoadFraudResults}

PROBLEM AREA:

When I call the LoadOrderQueueForm to bind the first observablecollection and later BindItemsSource to bind 2ed observable collection, everything works fine and no problem for the first time binding.

But, when I call BindItemsSource again to repopulate the obseravablecollection based on changed selected combo value via cmbWebsite_SelectionChanged, the observalblecollection gets populated with new value and LoadFraudResults property in viewmodule is populated with new values; but when i call the datacontext to rebind the datagrid,the datagrid does not reflect the changed values.

In other words the datagrid doesnot get changed when the datacontext is called the 2ed time in BindItemsSource method of the view.

manageFraudOrderViewModel.LoadOrders(website);
this.DataContext = manageFraudOrderViewModel;

manageFraudOrderViewModel values are correct but the datagrid is not relected with changed values.

Please help as I am stuck with this thing for past 2 days and the deadline is approaching near.

Thanks in advance

Answer 1

try to use datagrid.Items.Refresh() !

Answer 2

Hi Vikram, I am facing same problem now, 5 months later than you, I hope you had found its solutions, so plz tell how to re-populating the grid?

In my case I am doing paging using MVVM, if i can re-populating the datasource than my problem will be solved, so plz.

Thanks in advance.

Answer 3

Yes, ilu2009 is correct.

Binding using the MVVM modal to a DataGrid and changing the objects in DataGrid.ItemsSource requires DataGrid.ItemsSource.Refresh() for it to reflect on the UI.