Fix tests (#3068)

Author: jmprieur

tests/Microsoft.Identity.Web.Test/CacheEncryptionTests.cs

@@ -65,7 +65,7 @@ private byte[] GetFirstCacheValue(MemoryCache memoryCache)
                 .GetType()
                 .GetField("_entries", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic)
                 .GetValue(content1) as IDictionary)!;
-#elif NET8_0_OR_GREATER
+#elif NET8_0
             dynamic content1 = memoryCache
                 .GetType()
                 .GetField("_coherentState", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic)!
@@ -74,6 +74,15 @@ private byte[] GetFirstCacheValue(MemoryCache memoryCache)
                 .GetType()
                 .GetField("_stringEntries", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic)
                 .GetValue(content1) as IDictionary)!;
+#elif NET9_0_OR_GREATER
+            dynamic content1 = memoryCache
+                .GetType()
+                .GetField("_coherentState", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic)!
+                .GetValue(memoryCache)!;
+            memoryCacheContent = (content1?
+                .GetType()
+                .GetProperty("EntriesCollection", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic)
+                .GetValue(content1) as IDictionary)!;
 #else
             memoryCacheContent = (memoryCache
                 .GetType()