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    <p>The <code>INotifyPropertyChanged</code> interface <strong>is</strong> implemented with events. The interface has just one member, <code>PropertyChanged</code>, which is an event that consumers can subscribe to.</p> <p>The version that Richard posted is not safe. Here is how to safely implement this interface:</p> <pre><code>public class MyClass : INotifyPropertyChanged { private string imageFullPath; protected void OnPropertyChanged(PropertyChangedEventArgs e) { PropertyChangedEventHandler handler = PropertyChanged; if (handler != null) handler(this, e); } protected void OnPropertyChanged(string propertyName) { OnPropertyChanged(new PropertyChangedEventArgs(propertyName)); } public string ImageFullPath { get { return imageFullPath; } set { if (value != imageFullPath) { imageFullPath = value; OnPropertyChanged("ImageFullPath"); } } } public event PropertyChangedEventHandler PropertyChanged; } </code></pre> <p>Note that this does the following things:</p> <ul> <li><p>Abstracts the property-change notification methods so you can easily apply this to other properties;</p></li> <li><p>Makes a copy of the <code>PropertyChanged</code> delegate <strong>before</strong> attempting to invoke it (failing to do this will create a race condition).</p></li> <li><p>Correctly implements the <code>INotifyPropertyChanged</code> interface.</p></li> </ul> <p>If you want to <em>additionally</em> create a notification for a <em>specific</em> property being changed, you can add the following code:</p> <pre><code>protected void OnImageFullPathChanged(EventArgs e) { EventHandler handler = ImageFullPathChanged; if (handler != null) handler(this, e); } public event EventHandler ImageFullPathChanged; </code></pre> <p>Then add the line <code>OnImageFullPathChanged(EventArgs.Empty)</code> after the line <code>OnPropertyChanged("ImageFullPath")</code>.</p> <p>Since we have .Net 4.5 there exists the <a href="https://msdn.microsoft.com/en-us/library/system.runtime.compilerservices.callermembernameattribute.aspx" rel="noreferrer"><code>CallerMemberAttribute</code></a>, which allows to get rid of the hard-coded string for the property name in the source code:</p> <pre><code> protected void OnPropertyChanged( [System.Runtime.CompilerServices.CallerMemberName] string propertyName = "") { OnPropertyChanged(new PropertyChangedEventArgs(propertyName)); } public string ImageFullPath { get { return imageFullPath; } set { if (value != imageFullPath) { imageFullPath = value; OnPropertyChanged(); } } } </code></pre>
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    1. CO+1 for being the only person in this thread so far to get the null check on the event correct.
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    2. CO@Aaronaught: How to wire up the event-method with event?could you please explain.. I mean, where do I need to write the implementation for the event?
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