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POHow to create a custom observable collection using ConcurrentDictionary, INotifyCollectionChanged, INotifyPropertyChanged
 

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  1. POHow to create a custom observable collection using ConcurrentDictionary, INotifyCollectionChanged, INotifyPropertyChanged
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    <p>I am trying to create an ObservableConcurrentDictionary. This object will be used in a multithreaded application, and it's data is used to populate a control via the controls ItemsSource property.</p> <p>This is the implementation i have come up with:</p> <pre><code>public sealed class ObservableConcurrentDictionary&lt;TKey, TValue&gt; : ConcurrentDictionary&lt;TKey, TValue&gt;, INotifyCollectionChanged, INotifyPropertyChanged { #region Constructors public ObservableConcurrentDictionary() : base() { } public ObservableConcurrentDictionary(IEnumerable&lt;KeyValuePair&lt;TKey, TValue&gt;&gt; collection) : base(collection) { } public ObservableConcurrentDictionary(IEqualityComparer&lt;TKey&gt; comparer) : base(comparer) { } public ObservableConcurrentDictionary(int concurrencyLevel, int capacity) : base(concurrencyLevel, capacity) { } public ObservableConcurrentDictionary(IEnumerable&lt;KeyValuePair&lt;TKey, TValue&gt;&gt; collection, IEqualityComparer&lt;TKey&gt; comparer) : base(collection, comparer) { } public ObservableConcurrentDictionary(int concurrencyLevel, int capacity, IEqualityComparer&lt;TKey&gt; comparer) : base(concurrencyLevel, capacity, comparer) { } public ObservableConcurrentDictionary(int concurrencyLevel, IEnumerable&lt;KeyValuePair&lt;TKey, TValue&gt;&gt; collection, IEqualityComparer&lt;TKey&gt; comparer) : base(concurrencyLevel, collection, comparer) { } #endregion #region Public Methods public new TValue AddOrUpdate(TKey key, Func&lt;TKey, TValue&gt; addValueFactory, Func&lt;TKey, TValue, TValue&gt; updateValueFactory) { // Stores the value TValue value; // If key exists if (base.ContainsKey(key)) { // Update value and raise event value = base.AddOrUpdate(key, addValueFactory, updateValueFactory); OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Replace)); } // Else if key does not exist else { // Add value and raise event value = base.AddOrUpdate(key, addValueFactory, updateValueFactory); OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add)); } // Returns the value return value; } public void Clear() { // Clear dictionary base.Clear(); // Raise event OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset)); } public new TValue GetOrAdd(TKey key, Func&lt;TKey, TValue&gt; valueFactory) { // Stores the value TValue value; // If key exists if (base.ContainsKey(key)) // Get value value = base.GetOrAdd(key, valueFactory); // Else if key does not exist else { // Add value and raise event value = base.GetOrAdd(key, valueFactory); OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add)); } // Return value return value; } public new TValue GetOrAdd(TKey key, TValue value) { // If key exists if (base.ContainsKey(key)) // Get value base.GetOrAdd(key, value); // Else if key does not exist else { // Add value and raise event base.GetOrAdd(key, value); OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add)); } // Return value return value; } public new bool TryAdd(TKey key, TValue value) { // Stores tryAdd bool tryAdd; // If added if (tryAdd = base.TryAdd(key, value)) // Raise event OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add)); // Return tryAdd return tryAdd; } public new bool TryRemove(TKey key, out TValue value) { // Stores tryRemove bool tryRemove; // If removed if (tryRemove = base.TryRemove(key, out value)) // Raise event OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove)); // Return tryAdd return tryRemove; } public bool TryUpdate(TKey key, TValue newValue, TValue comparisonValue) { // Stores tryUpdate bool tryUpdate; // If updated if (tryUpdate = base.TryUpdate(key, newValue, comparisonValue)) // Raise event OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Replace)); // Return tryUpdate return tryUpdate; } #endregion #region Private Methods private void OnCollectionChanged(NotifyCollectionChangedEventArgs e) { if (CollectionChanged != null) CollectionChanged(this, e); } #endregion #region INotifyCollectionChanged Members public event NotifyCollectionChangedEventHandler CollectionChanged; #endregion #region INotifyPropertyChanged Members public event PropertyChangedEventHandler PropertyChanged; #endregion } </code></pre> <p>Unfortunately the solution does not work as intended - in fact, it doesn't work at all. Any ideas on what i am doing wrong or do any better solutions exist?</p> <p>Please note i CAN'T USE ObservableCollection, hence i have to write my own Observable collection.</p> <p><strong>EDIT: The working version is below. Hope this helps someone else with a similar problem.</strong></p> <pre><code>public sealed class ObservableConcurrentDictionary&lt;TKey, TValue&gt; : ConcurrentDictionary&lt;TKey, TValue&gt;, INotifyCollectionChanged, INotifyPropertyChanged { public ObservableConcurrentDictionary() : base() { } public ObservableConcurrentDictionary(IEnumerable&lt;KeyValuePair&lt;TKey, TValue&gt;&gt; collection) : base(collection) { } public ObservableConcurrentDictionary(IEqualityComparer&lt;TKey&gt; comparer) : base(comparer) { } public ObservableConcurrentDictionary(int concurrencyLevel, int capacity) : base(concurrencyLevel, capacity) { } public ObservableConcurrentDictionary(IEnumerable&lt;KeyValuePair&lt;TKey, TValue&gt;&gt; collection, IEqualityComparer&lt;TKey&gt; comparer) : base(collection, comparer) { } public ObservableConcurrentDictionary(int concurrencyLevel, int capacity, IEqualityComparer&lt;TKey&gt; comparer) : base(concurrencyLevel, capacity, comparer) { } public ObservableConcurrentDictionary(int concurrencyLevel, IEnumerable&lt;KeyValuePair&lt;TKey, TValue&gt;&gt; collection, IEqualityComparer&lt;TKey&gt; comparer) : base(concurrencyLevel, collection, comparer) { } public new TValue AddOrUpdate(TKey key, Func&lt;TKey, TValue&gt; addValueFactory, Func&lt;TKey, TValue, TValue&gt; updateValueFactory) { // Stores the value TValue value; // If key exists if (base.ContainsKey(key)) { // Update value and raise event value = base.AddOrUpdate(key, addValueFactory, updateValueFactory); OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Replace, value)); } // Else if key does not exist else { // Add value and raise event value = base.AddOrUpdate(key, addValueFactory, updateValueFactory); OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, value)); } // Returns the value return value; } public new void Clear() { // Clear dictionary base.Clear(); // Raise event OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset)); } public new TValue GetOrAdd(TKey key, Func&lt;TKey, TValue&gt; valueFactory) { // Stores the value TValue value; // If key exists if (base.ContainsKey(key)) // Get value value = base.GetOrAdd(key, valueFactory); // Else if key does not exist else { // Add value and raise event value = base.GetOrAdd(key, valueFactory); OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, value)); } // Return value return value; } public new TValue GetOrAdd(TKey key, TValue value) { // If key exists if (base.ContainsKey(key)) // Get value base.GetOrAdd(key, value); // Else if key does not exist else { // Add value and raise event base.GetOrAdd(key, value); OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, value)); } // Return value return value; } public new bool TryAdd(TKey key, TValue value) { // Stores tryAdd bool tryAdd; // If added if (tryAdd = base.TryAdd(key, value)) // Raise event OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, value)); // Return tryAdd return tryAdd; } public new bool TryRemove(TKey key, out TValue value) { // Stores tryRemove bool tryRemove; // If removed if (tryRemove = base.TryRemove(key, out value)) // Raise event OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, value)); // Return tryAdd return tryRemove; } public new bool TryUpdate(TKey key, TValue newValue, TValue comparisonValue) { // Stores tryUpdate bool tryUpdate; // If updated if (tryUpdate = base.TryUpdate(key, newValue, comparisonValue)) // Raise event OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Replace, newValue)); // Return tryUpdate return tryUpdate; } private void OnCollectionChanged(NotifyCollectionChangedEventArgs e) { if (CollectionChanged != null) CollectionChanged(this, e); } public event NotifyCollectionChangedEventHandler CollectionChanged; public event PropertyChangedEventHandler PropertyChanged; } </code></pre>
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    1. CO"it doesn't work at all" - is not valid problem description. Please tell us what errors are you getting, what code are you using to test it and your reason why you cant use ObservableCollection.
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