peass-ng/PEASS-ng · error · ArgumentException

Type '{typeof(T).FullName}' doesn't have the 'Flags' attribu

Error message

Type '{typeof(T).FullName}' doesn't have the 'Flags' attribute

What it means

CheckIsEnum<T>(checkHasFlags: true) additionally throws ArgumentException when T is an enum but lacks the [Flags] attribute. It is a validation sentinel fired by bit-manipulation helpers (like BitPosition) that require a flags-style enum, so the at-fault input is a non-flags enum type argument.

Source

Thrown at winPEAS/winPEASexe/winPEAS/TaskScheduler/EnumUtil.cs:14

using System;
using System.Collections.Generic;
using System.ComponentModel;

namespace winPEAS.TaskScheduler
{
    internal static class EnumUtil
    {
        public static void CheckIsEnum<T>(bool checkHasFlags = false)
        {
            if (!typeof(T).IsEnum)
                throw new ArgumentException($"Type '{typeof(T).FullName}' is not an enum");
            if (checkHasFlags && !IsFlags<T>())
                throw new ArgumentException($"Type '{typeof(T).FullName}' doesn't have the 'Flags' attribute");
        }

        public static bool IsFlags<T>() => Attribute.IsDefined(typeof(T), typeof(FlagsAttribute));

        public static void CheckHasValue<T>(T value, string argName = null)
        {
            CheckIsEnum<T>();
            if (IsFlags<T>())
            {
                var allFlags = 0L;
                foreach (T flag in Enum.GetValues(typeof(T)))
                    allFlags |= Convert.ToInt64(flag);
                if ((allFlags & Convert.ToInt64(value)) != 0L)
                    return;
            }
            else if (Enum.IsDefined(typeof(T), value))
                return;
            throw new InvalidEnumArgumentException(argName ?? "value", Convert.ToInt32(value), typeof(T));

View on GitHub (pinned to 53fb989abc)

Solutions

1. Decorate the enum type with the [Flags] attribute before using it with bit-operation helpers.
2. Only pass enums that are semantically bit masks (e.g. TaskRunFlags) to methods requiring flags.
3. Check Attribute.IsDefined(typeof(T), typeof(FlagsAttribute)) before calling when the flags requirement is uncertain.

When it happens

Trigger: Thrown at winPEAS/winPEASexe/winPEAS/TaskScheduler/EnumUtil.cs:14 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of peass-ng/PEASS-ng@53fb989abc (2026-09-02). Data as JSON: /api/errors/c551a46660e40e73. Report an issue: GitHub.