Throw the correct exception type

Author: Vectorial1024

DictionaryList/DictionaryList.cs

@@ -80,6 +80,11 @@ public TValue this[int index]
             }
             set
             {
+                if ((uint)index >= (uint)_list.Count)
+                {
+                    // out of range!
+                    ThrowHelper.ThrowArgumentOutOfRangeException(index);
+                }
                 if (!_issetLookup[index])
                 {
                     // adding items during iteration is not allowed!

DictionaryList/ThrowHelper.cs

@@ -10,5 +10,11 @@ public static void ThrowBadEnumerationException()
         {
             throw new InvalidOperationException("Collection was modified; enumeration operation may not execute.");
         }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void ThrowArgumentOutOfRangeException(int index)
+        {
+            throw new ArgumentOutOfRangeException(nameof(index));
+        }
     }
 }