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“"This type of CollectionView does not support changes to its SourceCollection from a thread different from the Dispatcher thread."” Code Answer

"This type of CollectionView does not support changes to its SourceCollection from a thread different from the Dispatcher thread."

csharp by Solstice

on Dec 09 2020 Comment

//this exception is thrown because ObservableCollections (OCs) cannot have their
//collections modified from any thread but the UI thread. See linked source.
// -- To make OCs thread-safe in WPF 4.5+ :

//as a field in class where OC is instantiated:
using System.Collections.ObjectModel; 	//for ObservableCollection<T>
using System.Windows.Data;				//for BindingOperations
using System.Windows;
using System.Threading;

public static object m_lockObject;		//NOTE: One lockObject per collection!
public static ObservableCollection<T> m_OC;

//where OC is created (typically the constructor)
OC = new ObservableCollection<T>();
BindingOperations.EnableCollectionSynchronization(m_OC, m_lockObject);
Application.Current.Dispatcher.BeginInvoke(
  		DispatcherPriority.Send,
  		new Action(() => {
        BindingOperations.EnableCollectionSynchronization(m_OC, m_lockObject);
		}));
//the call of the EnableCollectionSynchronization MUST happen on the UI thread.
//This Dispatcher action ensures that it does.

//-- FINALLY --
//when altering OC will trigger OnPropertyChanged (.Add(), .Clear(), etc.)
//encase such statements within a lock using that OC's lockObject
lock (m_lockObject)
{
  m_OC.Add(null);
}

Source: www.jonathanantoine.com

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