--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/SilverlightValidation/SilverlightValidation.Tests/TestSupport/NotifyPropertyChangedEventWatcher.cs	Sat May 05 16:39:00 2012 +0100
@@ -0,0 +1,103 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using System.Globalization;
+using System.Linq.Expressions;
+
+namespace SilverlightValidation.Tests.TestSupport
+{
+    /// <summary>
+    ///   A helper class used by NotifyPropertyChangedAssertHelper to monitor PropertyChangedEvent notifications.
+    /// </summary>
+    public class NotifyPropertyChangedEventWatcher : Disposable
+    {
+        private readonly Dictionary<string, int> _raisedCounts = new Dictionary<string, int>();
+
+        // A reference to the instance of the class implementing INotifyPropertyChanged
+        private INotifyPropertyChanged _model;
+
+        /// <summary>
+        ///   Initializes a new instance of the <see cref = "NotifyPropertyChangedEventWatcher" /> class.
+        /// </summary>
+        /// <param name = "model">The model.</param>
+        public NotifyPropertyChangedEventWatcher(INotifyPropertyChanged model)
+        {
+            if (model == null) throw new ArgumentNullException("model");
+
+            _model = model;
+            _model.PropertyChanged += OnPropertyChanged;
+        }
+
+        [SuppressMessage("Microsoft.Design", "CA1011:ConsiderPassingBaseTypesAsParameters"),
+         SuppressMessage("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures")]
+        public int GetRaisedCount<T>(Expression<Func<T>> propertyExpression)
+        {
+            return GetRaisedCount(PropertySupport.ExtractPropertyName(propertyExpression));
+        }
+
+        public int GetRaisedCount(string propertyName)
+        {
+            propertyName = string.IsNullOrEmpty(propertyName) ? string.Empty : propertyName;
+
+            PropertySupport.VerifyPropertyName(_model, propertyName);
+
+            return _raisedCounts.ContainsKey(propertyName) ? _raisedCounts[propertyName] : 0;
+        }
+
+        private void RecordPropertyChanged(string propertyName)
+        {
+            if (_raisedCounts.ContainsKey(propertyName))
+            {
+                _raisedCounts[propertyName]++;
+            }
+            else
+            {
+                _raisedCounts[propertyName] = 1;
+            }
+        }
+
+        /// <summary>
+        ///   The OnPropertyChanged event handler.
+        /// </summary>
+        /// <remarks>
+        ///   Records how many times the monitored property name has changed.
+        /// </remarks>
+        private void OnPropertyChanged(object sender, PropertyChangedEventArgs eventArgs)
+        {
+            // If PropertyName is null or string.Empty then it's the 'all properties' changed event.
+            RecordPropertyChanged(string.IsNullOrEmpty(eventArgs.PropertyName) ? string.Empty : eventArgs.PropertyName);
+        }
+
+        /// <summary>
+        ///   Releases unmanaged and - optionally - managed resources
+        /// </summary>
+        /// <param name = "disposing"><c>true</c> to release both managed and unmanaged resources; <c>false</c> to release only unmanaged resources.</param>
+        protected override void Dispose(bool disposing)
+        {
+            if (null != _model)
+            {
+                var model = _model;
+                _model = null;
+                model.PropertyChanged -= OnPropertyChanged;
+            }
+        }
+
+        /// <summary>
+        ///   Traces the event counts.
+        /// </summary>
+        [Conditional("DEBUG")]
+        public void TraceEventCounts()
+        {
+            foreach (var pair in _raisedCounts)
+            {
+                string name = string.IsNullOrEmpty(pair.Key) ? "all properties" : pair.Key;
+                int value = pair.Value;
+
+                Debug.WriteLine(string.Format(
+                    CultureInfo.InvariantCulture, @"Property '{0}' raised {1} times.", name, value));
+            }
+        }
+    }
+}
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