aspnetboilerplate/aspnetboilerplate · error · ArgumentException

' ' is a key field and cannot be marked readonly.

Error message

'{0}' is a key field and cannot be marked readonly.

What it means

Guard in MemberMap.ReadOnly(): the member {0} has a KeyType other than NotAKey and SlapperIdentifierKey, i.e. it is an active key field. Marking a key read-only would prevent the mapper from writing key values during insert/update, so the fluent ReadOnly() call is rejected with this ArgumentException.

Solutions

1. Do not call ReadOnly() on a key member; apply ReadOnly() only to non-key properties.
2. Move the key mapping to a writable property and keep {0} read-only if it must not be persisted.
3. Skip the ReadOnly() call for key members and control write behavior at the database/key-generation level instead.

When it happens

Trigger: Thrown at src/Abp.Dapper/Dapper-Extensions/Mapper/MemberMap.cs:197 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of aspnetboilerplate/aspnetboilerplate@2323c13a15 (2026-09-08). Data as JSON: /api/errors/562be5b19855ccd3. Report an issue: GitHub.

Appendix: source

Thrown at src/Abp.Dapper/Dapper-Extensions/Mapper/MemberMap.cs:197

        public MemberMap Ignore()
        {
            if (KeyType != KeyType.NotAKey && KeyType != KeyType.SlapperIdentifierKey)
            {
                throw new ArgumentException(string.Format("'{0}' is a key field and cannot be ignored.", Name));
            }

            Ignored = true;
            return this;
        }

        /// <summary>
        /// Fluently sets the read-only status of the property.
        /// </summary>
        public MemberMap ReadOnly()
        {
            if (KeyType != KeyType.NotAKey && KeyType != KeyType.SlapperIdentifierKey)
            {
                throw new ArgumentException(string.Format("'{0}' is a key field and cannot be marked readonly.", Name));
            }

            IsReadOnly = true;
            return this;
        }

        /// <summary>
        /// Fluently sets the field length of the property
        /// </summary>
        /// <param name="size">The length of the field as it exists in the database</param>
        public MemberMap Size(int size)
        {
            if (size < 0)
            {
                throw new ArgumentException(string.Format("'{0}' cannot have a negative field length.", Name));
            }

            DbSize = size;

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