Validate dictionary method calls using PredefinedMethodsHelper

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: StefH

src/System.Linq.Dynamic.Core/Parser/ExpressionParser.cs

@@ -2324,6 +2324,11 @@ private bool TryParseEnumerable(Expression instance, Type enumerableType, string
         if (type != null && TypeHelper.IsDictionary(type) && _methodFinder.ContainsMethod(type, methodName, false))
         {
             var dictionaryMethod = type.GetMethod(methodName)!;
+            if (!PredefinedMethodsHelper.IsPredefinedDictionaryMethod(dictionaryMethod))
+            {
+                throw ParseError(tokenPos, Res.MethodIsInaccessible, methodName, TypeHelper.GetTypeName(dictionaryMethod.DeclaringType!));
+            }
+
             expression = Expression.Call(instance, dictionaryMethod, args);
             return true;
         }

src/System.Linq.Dynamic.Core/Parser/PredefinedMethodsHelper.cs

@@ -20,6 +20,15 @@ internal static class PredefinedMethodsHelper
         ObjectStaticReferenceEquals
     ];
 
+    private static readonly HashSet<string> AllowedDictionaryMethodNames = ["ContainsKey", "ContainsValue", "TryGetValue", "get_Item"];
+
+    public static bool IsPredefinedDictionaryMethod(MethodInfo method)
+    {
+        Check.NotNull(method);
+
+        return AllowedDictionaryMethodNames.Contains(method.Name);
+    }
+
     public static bool IsPredefinedMethod(ParsingConfig config, MemberInfo member)
     {
         Check.NotNull(config);