1 files changed, 35 insertions, 0 deletions
diff --git a/src/mscorlib/src/System/CurrentSystemTimeZone.Cache.cs b/src/mscorlib/src/System/CurrentSystemTimeZone.Cache.cs
new file mode 100644
index 0000000000..744c697124
--- /dev/null
+++ b/src/mscorlib/src/System/CurrentSystemTimeZone.Cache.cs
@@ -0,0 +1,35 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections;
+using System.Globalization;
+
+namespace System
+{
+    internal partial class CurrentSystemTimeZone
+    {
+        private DaylightTime GetCachedDaylightChanges(int year)
+        {
+            Object objYear = (Object)year;
+
+            if (!m_CachedDaylightChanges.Contains(objYear))
+            {
+                DaylightTime currentDaylightChanges = CreateDaylightChanges(year);
+                lock (m_CachedDaylightChanges)
+                {
+                    if (!m_CachedDaylightChanges.Contains(objYear))
+                    {
+                        m_CachedDaylightChanges.Add(objYear, currentDaylightChanges);
+                    }
+                }
+            }
+
+            return (DaylightTime)m_CachedDaylightChanges[objYear];
+        }
+
+        // The per-year information is cached in in this instance value. As a result it can
+        // be cleaned up by CultureInfo.ClearCachedData, which will clear the instance of this object
+        private readonly Hashtable m_CachedDaylightChanges = new Hashtable();
+    }
+}