abpframework/abp · error · ArgumentException

Given type ( ) should be instance of

Error message

Given type ({item.AssemblyQualifiedName}) should be instance of {typeof(TBaseType).AssemblyQualifiedName} 

What it means

Thrown by TypeList<TBaseType>.CheckType when an item added to a strongly-typed TypeList is not assignable to the list's TBaseType constraint (checked via TypeInfo.IsAssignableFrom). It is an ArgumentException naming 'item' and reports both the offending and expected AssemblyQualifiedNames.

Solutions

1. Confirm item inherits or implements TBaseType; fix the type being registered.
2. If TBaseType is too narrow for your need, widen the generic constraint on the list or use a plain List<Type>.
3. Add a compile-time guard by filtering candidate types through typeof(TBaseType).IsAssignableFrom(t) before Add.
4. Verify the plugin assembly matches the host framework version so the expected base type is present.

Example fix

// before
list.Add(typeof(SomeUnrelatedClass));

// after
if (typeof(TBaseType).IsAssignableFrom(typeof(SomeRelatedClass)))
{
    list.Add(typeof(SomeRelatedClass));
}

static bool CanAdd<TBaseType>(Type t)
    => typeof(TBaseType).IsAssignableFrom(t);

if (CanAdd<IMyContract>(candidate)) list.Add(candidate);

static bool IsKindOf<TBase>(Type t) => typeof(TBase).IsAssignableFrom(t);

try
{
    list.Add(candidate);
}
catch (ArgumentException ex) when (ex.ParamName == nameof(candidate))
{
    logger.LogWarning("Rejected non-conforming type {Type}", candidate);
}

When it happens

Trigger: Calling Add/Insert on a TypeList<TBaseType> (or a class deriving from it, e.g. a module's ContributionTypes) with a Type that does not inherit/implement TBaseType.

Common situations: Registering a contributor type that is missing the required interface, a plugin assembly returning a type that no longer implements the expected base after a refactor, or a copy-paste of the wrong concrete class.

Related errors

• Given module instance
• Given type is not an ABP module
• has a default value!
• is null!
• targetIndex should be between 0 and

AI-assisted analysis of abpframework/abp@7ed43b1931 (2026-08-13). Data as JSON: /api/errors/70e2a1631c2e92d6. Report an issue: GitHub.

Appendix: source

Thrown at framework/src/Volo.Abp.Core/Volo/Abp/Collections/TypeList.cs:149

        _typeList.CopyTo(array, arrayIndex);
    }

    /// <inheritdoc/>
    public IEnumerator<Type> GetEnumerator()
    {
        return _typeList.GetEnumerator();
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return _typeList.GetEnumerator();
    }

    private static void CheckType(Type item)
    {
        if (!typeof(TBaseType).GetTypeInfo().IsAssignableFrom(item))
        {
            throw new ArgumentException($"Given type ({item.AssemblyQualifiedName}) should be instance of {typeof(TBaseType).AssemblyQualifiedName} ", nameof(item));
        }
    }
}

View on GitHub (pinned to 7ed43b1931)