wpf datagrid not updating after change to observable collection

Question

wpf datagrid not updating after change to observable collection

Marc Jeeves 386

Hi All,

My Delete and add methods work fine, the Update is calling the HTTPPut and changing the data but i cant get the WPF form to update the same way i have been updating with add and delete.

My class is implementing INotifyPropertyChanged and i have the OnPropertyChanged method.

is there a better way to update the observable collection for add and delete that will fix update?
Thanks
Madaxe

//----------------------------------------------------------

protected void OnPropertyChanged([CallerMemberName] string propertyName = &#34;&#34;)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }

//----------------------------------------------------------

        public void UpdateContinent(string iNewContinentName, int iContinentObjectId)
        {
            Task&lt;ContinentModel&gt; TaskContinentModel = this.UpdateExistingContinent(iNewContinentName, iContinentObjectId);
            ObservableCollection&lt;ContinentModel&gt; NewContinentModels = _ContinentModels;
            ContinentModel UpdatedContinentModel = TaskContinentModel.Result;

            NewContinentModels.Where(w =&gt; w.objectID == UpdatedContinentModel.objectID).ToList().ForEach(i =&gt; i.continentName = iNewContinentName);

            this.ContinentModels = NewContinentModels;
        }

        private async Task&lt;ContinentModel&gt; UpdateExistingContinent(string iNewContinentName, int iContinentObjectId)
        {
            ContinentModel ReturnContinentModel = null;

//----------------------------------------------------------

        public void CreateContinent(string iContinentName)
        {
            Task&lt;ContinentModel&gt; TaskContinentModel = this.CreateNewContinent(iContinentName);
            ObservableCollection&lt;ContinentModel&gt; NewContinentModels = _ContinentModels;
            NewContinentModels.Add(TaskContinentModel.Result);
            this.ContinentModels = NewContinentModels;
        }


        private async Task&lt;ContinentModel&gt; CreateNewContinent(string iContinentName)
        {
            ContinentModel ReturnContinentModel = null;

//----------------------------------------------------------

2 answers

Your answer

Answer 1

Marc Jeeves 386

CollectionViewSource.GetDefaultView(DGD_UserList.ItemsSource).Refresh();

this works once i added this

Peter Fleischer (former MVP) 19,341 Reputation points

2020-03-22T14:05:10.13+00:00

Hi,
I cannot see this lines in your code.
Doubled Mioko 11 Reputation points

2020-06-05T13:32:07.6+00:00

Thanks, it really works!

Doubled Mioko 11

Hello. This is how my wpf app works:

View:

<DataGrid ItemsSource="{Binding Items}" SelectedItem="{Binding SelectedItem}" />
<Button Command="{Binding Button_Update}" />

ViewModel:

public ObservableCollection<T> Items { get; private set; }

public T SelectedItem
{
    get => GetValue<T>();
    set => SetValue(value, OnSelectedItemChanged);
}
...
Button_Update = new DelegateCommand(() =>
{
     UpdateSelectedItem();

     DbContext.Update(SelectedItem);
     DbContext.SaveChanges();

     CollectionViewSource.GetDefaultView(Items).Refresh();
}

Nico Dreyer 1 Reputation point

2020-12-12T19:07:51.22+00:00

When working with Observable Collections, either MVC or MVVM, make sure that you implement INotifyPropertyChanged on both the Model Classes and Controllers / ViewModels. This will enable binding context to automatically update the view once you change a value in it, if you are specifying the OnPropertyChange in the setter part of the Controller / ViewModels properties.
There are some easier implementations of these for example https://github.com/Fody/PropertyChanged. It is available on the Nuget Manager.

Answer 2

Peter Fleischer (former MVP) 19,341

Hi, change your update method (assign !)

public void UpdateContinent(string iNewContinentName, int iContinentObjectId)
{
Task<ContinentModel> TaskContinentModel = this.UpdateExistingContinent(iNewContinentName, iContinentObjectId);
ObservableCollection < ContinentModel> NewContinentModels = _ContinentModels;
ContinentModel UpdatedContinentModel = TaskContinentModel.Result;

this.ContinentModels = NewContinentModels.Where(w => w.objectID == UpdatedContinentModel.objectID).ToList().ForEach(i => i.continentName = iNewContinentName);
}

Marc Jeeves 386 Reputation points

2020-03-21T21:08:33.6+00:00

I tried this earlier and get this error, that's why i did it in two steps.

Severity Code Description Project File Line Suppression State
Error CS0029 Cannot implicitly convert type 'void' to 'System.Collections.ObjectModel.ObservableCollection<InfarstructureProject.Models.ContinentModel>' ImplementationProject C:\Users\ma_je\Desktop\LekoCustom\LekoCustomSolution\ImplementationProject\Implementation\CustomDataContinentImplementation.cs 135 Active
Peter Fleischer (former MVP) 19,341 Reputation points

2020-03-22T08:52:01.177+00:00

Hi, show code in line 135.

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wpf datagrid not updating after change to observable collection

2 answers

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