Entity framework Automapper Projectto无法使用struct创建映射表达式

在使用ProjectTo进行查询时，是否有一种方法可以支持将“包装”的域模型作为映射中的结构？ 例如，我有一个名为Edition的结构，它表示许可证版本。在数据库中，该列存储为

整数

。但是，在使用WebApi时，此类字段将作为结构版返回。您可能会问，如果它是WebApi，只需在模型中返回int即可。好的，这就是我们在封面下所做的，但是我们也有一个用于api的SDK，在这个SDK中，我们对返回的类进行建模，使其具有

Edition

，而不是

int

，因此开发人员很清楚数据的含义。 我们已经创建了.net

TypeConverters

和Newtonjson转换器，除了

AutoMapper

在使用

ProjectTo

Edition+EditionTypeConverter

[TypeConverter(typeof(EditionTypeConverter))]
    [Serializable]
    public struct Edition : ISerializable
    {
        /// <summary>
        /// Prefer using <see cref="Edition.Community"/> instead.
        /// This only exists to support using <see cref="Edition"/> on <see cref="System.Attribute"/>.
        /// </summary>
        public const int CommunityNumber = 1024;
        /// <summary>
        /// Prefer using <see cref="Edition.Standard"/> instead.
        /// This only exists to support using <see cref="Edition"/> on <see cref="System.Attribute"/>.
        /// </summary>
        public const int StandardNumber = 1025;
        /// <summary>
        /// Prefer using <see cref="Edition.Enterprise"/> instead.
        /// This only exists to support using <see cref="Edition"/> on <see cref="System.Attribute"/>.
        /// </summary>
        public const int EnterpriseNumber = 1026;
        public static readonly Edition NotLicensed = new Edition(0);
        public static readonly Edition Community = new Edition(CommunityNumber);
        public static readonly Edition Standard = new Edition(StandardNumber);
        public static readonly Edition Enterprise = new Edition(EnterpriseNumber);
        private readonly int edition;

        public Edition(int edition)
        {
            this.edition = edition;
        }

        public Edition(SerializationInfo info, StreamingContext context)
        {
            edition = (int)info.GetValue(nameof(edition), typeof(int));
        }

        public override string ToString()
        {
            if (edition == NotLicensed)
                return "Not Licensed";
            if (edition == Community)
                return nameof(Community);
            if (edition == Standard)
                return nameof(Standard);
            if (edition == Enterprise)
                return nameof(Enterprise);

            return $"Unknown({edition})";
        }

        public override bool Equals(object obj)
        {
            if (obj == null)
                return false;
            if (!(obj is Edition))
                return false;

            var token = (Edition)obj;
            return token.edition == edition;
        }

        public override int GetHashCode() => edition.GetHashCode();

        void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)
        {
            info.AddValue(nameof(edition), edition);
        }

        public static bool operator !=(Edition left, Edition right) => !(left == right);
        public static implicit operator int(Edition edition) => edition.edition;
        public static bool operator ==(Edition left, Edition right)
        {
            if (ReferenceEquals(left, null))
                return ReferenceEquals(right, null);

            return left.Equals(right);
        }

        public static Edition? From(int? edition) => edition.HasValue ? new Edition(edition.Value) : (Edition?)null;

        public class EditionTypeConverter : TypeConverter
        {
            public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
            {
                return sourceType.GetActualType() == typeof(int) ||
                    sourceType.GetActualType() == typeof(long) ||
                    base.CanConvertFrom(context, sourceType);
            }

            public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
            {
                if (value == null)
                    return null;

                if (int.TryParse(value.ToString(), out int edition))
                    return new Edition(edition);
                if (long.TryParse(value.ToString(), out long longEdition))
                    return new Edition((int)longEdition);

                return base.ConvertFrom(context, culture, value);
            }
        }
    }

context.ScriptVersions.Where(predicate).ProjectTo<ScriptVersionModel>();

ScriptVersion-映射到数据库的实体框架类

public class ScriptVersion
{
   public int? License{get;set;}
}

触发错误的代码

[TypeConverter(typeof(EditionTypeConverter))]
    [Serializable]
    public struct Edition : ISerializable
    {
        /// <summary>
        /// Prefer using <see cref="Edition.Community"/> instead.
        /// This only exists to support using <see cref="Edition"/> on <see cref="System.Attribute"/>.
        /// </summary>
        public const int CommunityNumber = 1024;
        /// <summary>
        /// Prefer using <see cref="Edition.Standard"/> instead.
        /// This only exists to support using <see cref="Edition"/> on <see cref="System.Attribute"/>.
        /// </summary>
        public const int StandardNumber = 1025;
        /// <summary>
        /// Prefer using <see cref="Edition.Enterprise"/> instead.
        /// This only exists to support using <see cref="Edition"/> on <see cref="System.Attribute"/>.
        /// </summary>
        public const int EnterpriseNumber = 1026;
        public static readonly Edition NotLicensed = new Edition(0);
        public static readonly Edition Community = new Edition(CommunityNumber);
        public static readonly Edition Standard = new Edition(StandardNumber);
        public static readonly Edition Enterprise = new Edition(EnterpriseNumber);
        private readonly int edition;

        public Edition(int edition)
        {
            this.edition = edition;
        }

        public Edition(SerializationInfo info, StreamingContext context)
        {
            edition = (int)info.GetValue(nameof(edition), typeof(int));
        }

        public override string ToString()
        {
            if (edition == NotLicensed)
                return "Not Licensed";
            if (edition == Community)
                return nameof(Community);
            if (edition == Standard)
                return nameof(Standard);
            if (edition == Enterprise)
                return nameof(Enterprise);

            return $"Unknown({edition})";
        }

        public override bool Equals(object obj)
        {
            if (obj == null)
                return false;
            if (!(obj is Edition))
                return false;

            var token = (Edition)obj;
            return token.edition == edition;
        }

        public override int GetHashCode() => edition.GetHashCode();

        void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)
        {
            info.AddValue(nameof(edition), edition);
        }

        public static bool operator !=(Edition left, Edition right) => !(left == right);
        public static implicit operator int(Edition edition) => edition.edition;
        public static bool operator ==(Edition left, Edition right)
        {
            if (ReferenceEquals(left, null))
                return ReferenceEquals(right, null);

            return left.Equals(right);
        }

        public static Edition? From(int? edition) => edition.HasValue ? new Edition(edition.Value) : (Edition?)null;

        public class EditionTypeConverter : TypeConverter
        {
            public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
            {
                return sourceType.GetActualType() == typeof(int) ||
                    sourceType.GetActualType() == typeof(long) ||
                    base.CanConvertFrom(context, sourceType);
            }

            public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
            {
                if (value == null)
                    return null;

                if (int.TryParse(value.ToString(), out int edition))
                    return new Edition(edition);
                if (long.TryParse(value.ToString(), out long longEdition))
                    return new Edition((int)longEdition);

                return base.ConvertFrom(context, culture, value);
            }
        }
    }

context.ScriptVersions.Where(predicate).ProjectTo<ScriptVersionModel>();

context.ScriptVersions.Where（谓词）.ProjectTo（）；

您可以使用此

public IMapper InitializeMapper（）
{
var配置=新的MapperConfiguration（cfg=>
{
cfg.CreateMap（）.formMember（a=>a.License，map=>map.MapFrom（src=>newedition（src.License？？0））；
});
返回configuration.CreateMapper（）；
}

然后

var-mapper=InitializeMapper（）；
ScriptVersionModelEdition=mapper.Map（新的ScriptVersion{License=12}）；

或

context.ScriptVersions.Where（谓词）.ProjectTo（）；

CreateMap（）