fix accessibility issue

openxml4Net/Util/EnumExtensions.cs

@@ -0,0 +1,48 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace NPOI.OpenXml4Net.Util
+{
+    /// <summary>
+    /// This class provides helper methods that reduce dynamic code / reflection use, for better AOT performance.
+    /// </summary>
+    internal static class EnumExtensions
+    {
+#if !NET6_0_OR_GREATER
+        public static T[] GetEnumValues<T>() where T : struct, Enum
+        {
+            return (T[])Enum.GetValues(typeof(T));
+        }
+
+        public static string GetEnumName<T>(T val) where T : struct, Enum
+        {
+            return Enum.GetName(typeof(T), val);
+        }
+
+        public static string[] GetEnumNames<T>() where T : struct, Enum
+        {
+            return Enum.GetNames(typeof(T));
+        }
+#else
+        // AOT-friendly
+        public static T[] GetEnumValues<T>() where T : struct, Enum
+        {
+            return Enum.GetValues<T>();
+        }
+
+        public static string GetEnumName<T>(T val) where T : struct, Enum
+        {
+            return Enum.GetName<T>(val);
+        }
+
+        public static string[] GetEnumNames<T>() where T : struct, Enum
+        {
+            return Enum.GetNames<T>();
+        }
+#endif
+    }
+}