Fixes up the equality members for the event args types to include Gethash code and sequence equal checking, this is done by a base class used by event args that deal with collections.

src/Umbraco.Core/HashCodeHelper.cs

@@ -0,0 +1,101 @@
+using System.Collections.Generic;
+
+namespace Umbraco.Core
+{
+    /// <summary>
+    /// Borrowed from http://stackoverflow.com/a/2575444/694494
+    /// </summary>
+    internal static class HashCodeHelper
+    {
+        public static int GetHashCode<T1, T2>(T1 arg1, T2 arg2)
+        {
+            unchecked
+            {
+                return 31 * arg1.GetHashCode() + arg2.GetHashCode();
+            }
+        }
+
+        public static int GetHashCode<T1, T2, T3>(T1 arg1, T2 arg2, T3 arg3)
+        {
+            unchecked
+            {
+                int hash = arg1.GetHashCode();
+                hash = 31 * hash + arg2.GetHashCode();
+                return 31 * hash + arg3.GetHashCode();
+            }
+        }
+
+        public static int GetHashCode<T1, T2, T3, T4>(T1 arg1, T2 arg2, T3 arg3,
+            T4 arg4)
+        {
+            unchecked
+            {
+                int hash = arg1.GetHashCode();
+                hash = 31 * hash + arg2.GetHashCode();
+                hash = 31 * hash + arg3.GetHashCode();
+                return 31 * hash + arg4.GetHashCode();
+            }
+        }
+
+        public static int GetHashCode<T>(T[] list)
+        {
+            unchecked
+            {
+                int hash = 0;
+                foreach (var item in list)
+                {
+                    hash = 31 * hash + item.GetHashCode();
+                }
+                return hash;
+            }
+        }
+
+        public static int GetHashCode<T>(IEnumerable<T> list)
+        {
+            unchecked
+            {
+                int hash = 0;
+                foreach (var item in list)
+                {
+                    hash = 31 * hash + item.GetHashCode();
+                }
+                return hash;
+            }
+        }
+
+        /// <summary>
+        /// Gets a hashcode for a collection for that the order of items 
+        /// does not matter.
+        /// So {1, 2, 3} and {3, 2, 1} will get same hash code.
+        /// </summary>
+        public static int GetHashCodeForOrderNoMatterCollection<T>(
+            IEnumerable<T> list)
+        {
+            unchecked
+            {
+                int hash = 0;
+                int count = 0;
+                foreach (var item in list)
+                {
+                    hash += item.GetHashCode();
+                    count++;
+                }
+                return 31 * hash + count.GetHashCode();
+            }
+        }
+
+        /// <summary>
+        /// Alternative way to get a hashcode is to use a fluent 
+        /// interface like this:<br />
+        /// return 0.CombineHashCode(field1).CombineHashCode(field2).
+        ///     CombineHashCode(field3);
+        /// </summary>
+        public static int CombineHashCode<T>(this int hashCode, T arg)
+        {
+            unchecked
+            {
+                return 31 * hashCode + arg.GetHashCode();
+            }
+        }
+    }
+}