What causes "Content type name is reserved for internal use" in OrchardCMS/OrchardCore?

Rename the content type to a non-reserved name (prefix with your module/brand, e.g. 'MyModuleListItem')

OrchardCMS/OrchardCore · error · ArgumentException

Content type name is reserved for internal use

Error message

Content type name is reserved for internal use

What it means

ContentTypeDefinitionBuilder.Build() rejects content type names considered reserved for internal use via IsReservedContentName(). Orchard reserves names starting with prefixes like 'List', 'Container', or otherwise colliding with internal systems, to prevent ambiguity with framework-generated content types.

Solutions

Rename the content type to a non-reserved name (prefix with your module/brand, e.g. 'MyModuleListItem')
Reuse the built-in List/Container types instead of defining a colliding name
Update all references: migrations, recipes, placement.json, and queries that reference the old name

Example fix

// before
builder.AlterTypeDefinitionAsync("ListItem", t => t.WithDisplayName("List Item"));
// after
builder.AlterTypeDefinitionAsync("MyStoreListItem", t => t.WithDisplayName("List Item"));

Defensive patterns

Strategy: validation

Validate before calling

if (typeName.IsReservedContentName())
    throw new ArgumentException($"'{typeName}' is reserved for internal use; choose another name.");

Try / catch

try
{
    await builder.AlterTypeDefinitionAsync(name, configure);
}
catch (ArgumentException ex) when (ex.Message.Contains("reserved"))
{
    _logger.LogError(ex, "Content type name '{Name}' is reserved", name);
}

Prevention

Prefix custom type names with your module or brand to avoid reserved names like 'List*'
Check IsReservedContentName() in migrations before altering definitions
Reuse built-in List/Container types rather than shadowing them

When it happens

Trigger: Calling AlterTypeDefinitionAsync with a name matching a reserved pattern (e.g. names starting with 'List' or other reserved prefixes defined in StringExtensions.IsReservedContentName)

Common situations: Creating types like 'ListItem' or 'List' for custom listing features; renaming existing internal types; migrating legacy systems where 'List' was not reserved

Understand the failure class

Background: "invalid id" errors: invalid identifier format — why libraries reject IDs before lookup, and how to fix them — this error's family across 37 libraries.

Related errors

AI-assisted analysis of OrchardCMS/OrchardCore@4306c0717f (2026-09-13). Data as JSON: /api/errors/b43d43324d30a05d. Report an issue: GitHub.

Appendix: source

Thrown at src/OrchardCore/OrchardCore.ContentManagement.Abstractions/Metadata/Builders/ContentTypeDefinitionBuilder.cs:51

            _displayName = existing.DisplayName;
            _parts = existing.Parts.ToList();
            _settings = existing.Settings.Clone();
        }
    }

    public ContentTypeDefinition Build()
    {
        if (!char.IsLetter(_name[0]))
        {
            throw new ArgumentException("Content type name must start with a letter", "name");
        }
        if (!string.Equals(_name, _name.ToSafeName(), StringComparison.OrdinalIgnoreCase))
        {
            throw new ArgumentException("Content type name contains invalid characters", "name");
        }
        if (_name.IsReservedContentName())
        {
            throw new ArgumentException("Content type name is reserved for internal use", "name");
        }

        return new ContentTypeDefinition(_name, _displayName, _parts, _settings);
    }

    [Obsolete("This method has been deprecated, please use WithName() instead.")]
    public ContentTypeDefinitionBuilder Named(string name) => WithName(name);

    public ContentTypeDefinitionBuilder WithName(string name)
    {
        _name = name;

        return this;
    }

    [Obsolete("This method has been deprecated, please use WithDisplayName() instead.")]
    public ContentTypeDefinitionBuilder DisplayedAs(string displayName) => WithDisplayName(displayName);

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