添加项目文件。

Szmedi.RevitToolkit.Approval/Extensions/IEnumerableExtensions.cs

@@ -0,0 +1,24 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Szmedi.RevitToolkit.Approval.Extensions
+{
+    internal static class IEnumerableExtensions
+    {
+        public static IEnumerable<TSource> DistinctBy<TSource, TKey>
+            (this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
+        {
+            HashSet<TKey> seenKeys = new HashSet<TKey>();
+            foreach (TSource element in source)
+            {
+                if (seenKeys.Add(keySelector(element)))
+                {
+                    yield return element;
+                }
+            }
+        }
+    }
+}