JamesNK/Newtonsoft.Json · error · Exception

Cannot get attributes from '{0}'.

Error message

Cannot get attributes from '{0}'.

What it means

Thrown by ReflectionUtils.GetAttributes in the PORTABLE40 (legacy PCL) build when the attributeProvider object is not a Type, Assembly, MemberInfo, Module, or ParameterInfo. In the PORTABLE40 build there is no ICustomAttributeProvider fallback, so any unsupported provider hits this throw.

Source

Thrown at Src/Newtonsoft.Json/Utilities/ReflectionUtils.cs:826

                    return attributes;
                case Assembly a:
                    return (attributeType != null) ? Attribute.GetCustomAttributes(a, attributeType) : Attribute.GetCustomAttributes(a);
                case MemberInfo mi:
                    return (attributeType != null) ? Attribute.GetCustomAttributes(mi, attributeType, inherit) : Attribute.GetCustomAttributes(mi, inherit);
#if !PORTABLE40
                case Module m:
                    return (attributeType != null) ? Attribute.GetCustomAttributes(m, attributeType, inherit) : Attribute.GetCustomAttributes(m, inherit);
#endif
                case ParameterInfo p:
                    return (attributeType != null) ? Attribute.GetCustomAttributes(p, attributeType, inherit) : Attribute.GetCustomAttributes(p, inherit);
                default:
#if !PORTABLE40
                    ICustomAttributeProvider customAttributeProvider = (ICustomAttributeProvider)attributeProvider;
                    object[] result = (attributeType != null) ? customAttributeProvider.GetCustomAttributes(attributeType, inherit) : customAttributeProvider.GetCustomAttributes(inherit);

                    return (Attribute[])result;
#else
                    throw new Exception("Cannot get attributes from '{0}'.".FormatWith(CultureInfo.InvariantCulture, provider));
#endif
            }
        }
#else
        public static T[] GetAttributes<T>(object attributeProvider, bool inherit) where T : Attribute
        {
            return GetAttributes(attributeProvider, typeof(T), inherit).Cast<T>().ToArray();
        }

        public static Attribute[] GetAttributes(object provider, Type? attributeType, bool inherit)
        {
            switch (provider)
            {
                case Type t:
                    return (attributeType != null)
                        ? t.GetTypeInfo().GetCustomAttributes(attributeType, inherit).ToArray()
                        : t.GetTypeInfo().GetCustomAttributes(inherit).ToArray();
                case Assembly a:

View on GitHub (pinned to 4f73e74372)

Solutions

1. Pass a supported attribute provider (Type, MemberInfo, Assembly, Module, or ParameterInfo).
2. Migrate off the Portable40 build to netstandard2.0, which has the ICustomAttributeProvider fallback path.

Example fix

// before
var attrs = ReflectionUtils.GetAttributes(someRandomObject, null, false);

// after
var attrs = ReflectionUtils.GetAttributes(typeof(Foo), null, false);

if (provider is not Type and not MemberInfo and not Assembly and not Module and not ParameterInfo)
    throw new ArgumentException($"Unsupported attribute provider: {provider?.GetType()}");

static bool IsAttributeProvider(object o) => o is Type or MemberInfo or Assembly or Module or ParameterInfo;

When it happens

Trigger: Passing an arbitrary object (not one of the supported reflection providers) to GetAttributes while running the Portable40 build of Json.NET. The other builds fall back to ICustomAttributeProvider and only throw elsewhere (see error 278).

Common situations: Legacy PCL projects consuming the Portable40 build, custom attribute-reading helpers passing boxed values, or migrating from an old portable class library.

Related errors

• type
• Unexpected type code '{0}' for type '{1}'.
• Error setting value to '{0}' on '{1}'.
• Error getting value from '{0}' on '{1}'.
• Error setting value to '{0}' on '{1}'.

AI-assisted analysis of JamesNK/Newtonsoft.Json@4f73e74372 (2026-08-07). Data as JSON: /api/errors/7dd59f07f6089af1. Report an issue: GitHub.