Setting ComboBoxAdv.ItemsSource in a SfPropertyGrid Custom Editor results in a null reference error.

[NM van Strien]

Dear customer support team,

I am trying to create a custom editor for the SfPropertyGrid using a ComboBoxAdv control. The items are loaded from a database. When I try the set the ComboBoxAdv.ItemsSource I get a null reference exception. If I use the exact same code with a regular ComboBox, the ItemsSource is populated. Any ideas how to solve this would be helpful.

Thanks in advance,

NIels

Below is the error I get:

System.NullReferenceException

  HResult=0x80004003

  Message=Object reference not set to an instance of an object.

  Source=Syncfusion.Shared.WPF

  StackTrace:

   at Syncfusion.Windows.Tools.Controls.ComboBoxAdv.FilterItem(Object value)

   at System.Windows.Data.ListCollectionView.PrepareLocalArray()

   at System.Windows.Data.ListCollectionView.RefreshOverride()

   at System.Windows.Data.CollectionView.RefreshInternal()

   at System.Windows.Data.CollectionView.RefreshOrDefer()

   at System.Windows.Data.CollectionView.set_Filter(Predicate`1 value)

   at System.Windows.Data.ListCollectionView.set_Filter(Predicate`1 value)

   at Syncfusion.Windows.Tools.Controls.ComboBoxAdv.OnItemsSourceChanged(IEnumerable oldValue, IEnumerable newValue)

   at System.Windows.Controls.ItemsControl.OnItemsSourceChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)

   at System.Windows.DependencyObject.OnPropertyChanged(DependencyPropertyChangedEventArgs e)

   at System.Windows.FrameworkElement.OnPropertyChanged(DependencyPropertyChangedEventArgs e)

   at System.Windows.DependencyObject.NotifyPropertyChange(DependencyPropertyChangedEventArgs args)

   at System.Windows.DependencyObject.UpdateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, Boolean coerceWithDeferredReference, Boolean coerceWithCurrentValue, OperationType operationType)

   at System.Windows.DependencyObject.SetValueCommon(DependencyProperty dp, Object value, PropertyMetadata metadata, Boolean coerceWithDeferredReference, Boolean coerceWithCurrentValue, OperationType operationType, Boolean isInternal)

   at System.Windows.DependencyObject.SetValue(DependencyProperty dp, Object value)

   at System.Windows.Controls.ItemsControl.set_ItemsSource(IEnumerable value)

   at EPD3.Infrastructure.SFControls.SfPropertyGrid.CustomEditors.HealthProfessionalEditor.<combo_Loaded>d__14.MoveNext() in C:\Users\Niels\source\repos\SyncFusionDemoApp\EPD3\Infrastructure\SFControls\SfPropertyGrid\CustomEditors\HealthProfessionalEditor.cs:line 86

Below here is the code I have in my Editor:

using EPDMediatRLibrary.Models.API.AppData.V1.Contact.Person.Practitioner;

using EPDMediatRLibrary.Queries.API.AppData.V1.Contact.Person.Practitioner;

using Syncfusion.Windows.PropertyGrid;

using Syncfusion.Windows.Tools.Controls;

using System.Collections.ObjectModel;

using System.Reflection;

using System.Windows;

using System.Windows.Controls;

using System.Windows.Data;

namespace EPD3.Infrastructure.SFControls.SfPropertyGrid.CustomEditors

{

    internal class HealthProfessionalEditor : ITypeEditor

    {

        public IEnumerable<PractitionerHealthcareProviderCompanyDisplayModel> GPItemsSourceOrig { get; set; }

        private ObservableCollection<PractitionerHealthcareProviderCompanyDisplayModel> CBBItemsSource { get; set; }

        private ComboBoxAdv combo;

        private readonly IMediator _mediator;

        public HealthProfessionalEditor(IMediator mediator)

        {

            _mediator = mediator;

            CBBItemsSource = new();

        }

        public void Attach(PropertyViewItem property, PropertyItem info)

        {

            if (info.CanWrite)

            {

                var binding = new Binding("Value")

                {

                    Mode = BindingMode.TwoWay,

                    Source = info,

                    ValidatesOnExceptions = true,

                    ValidatesOnDataErrors = true

                };

                BindingOperations.SetBinding(combo, System.Windows.Controls.Primitives.Selector.SelectedItemProperty, binding);

                combo.IsTabStop = true;

                combo.IsHitTestVisible = true;

                combo.IsEnabled = true;

            }

            else

            {

                var binding = new Binding("Value")

                {

                    Source = info,

                    ValidatesOnExceptions = true,

                    ValidatesOnDataErrors = true

                };

                BindingOperations.SetBinding(combo, System.Windows.Controls.Primitives.Selector.SelectedItemProperty, binding);

                combo.IsTabStop = false;

                combo.IsHitTestVisible = false;

                combo.IsEnabled = false;

            }

        }

        public object Create(PropertyInfo PropertyInfo)

        {

            combo = new()

            {

                IsEditable = true,

                AutoCompleteMode = AutoCompleteModes.Suggest,

                DisplayMemberPath = "PractitionerDisplayName",

            };

            combo.Loaded += new RoutedEventHandler(combo_Loaded);

            return combo;

        }

        public void Detach(PropertyViewItem property)

        {

            //throw new NotImplementedException();

        }

        private async void combo_Loaded(object sender, RoutedEventArgs e)

        {

            CancellationToken cancellationToken = new();

            GPItemsSourceOrig = await _mediator.Send(new GetGeneralPractitionersHealthcareProviderCompanyDisplayModelsQuery(), cancellationToken);

            if (GPItemsSourceOrig != null && GPItemsSourceOrig.Any())

            {

                CBBItemsSource = new ObservableCollection<PractitionerHealthcareProviderCompanyDisplayModel>(Enumerable.DistinctBy(GPItemsSourceOrig, x => x.HealthcareProviderCompanyId));

                CBBItemsSource.Insert(0, new PractitionerHealthcareProviderCompanyDisplayModel() { HealthcareCompanyDisplayName = "" });

                combo.ItemsSource = CBBItemsSource; // here is where the error occurs

            }

        }

    }

}

[Sudharsan Narayanan]

Hi NM van Strien,

We have prepared the sample to replicate the issue that “ComboBox throws null exception” from our end and we are unable to reproduce the issue. So, can you please find the sample from the below,

Sample: https://www.syncfusion.com/downloads/support/forum/171314/ze/CustomEditor-sample-450372998

Please check the sample and let us know your concerns, If we are misunderstood the query, Please modify the sample and revert to us with reproducible issue. So, it will be helpful to prompt the solution on further.

Regards,
Sudharsan

[NM van Strien]

Thank you! Probably there is something wrong with my code then. If I run into this problem again, I will report it here.

Kind regards,

Niels van Strien