Fluent composite key nested column issue

[Fred]

I am having an issue with the fluent mapping for a composite key:

Database structure:

TABLE `Contact` (
  `ContactId` int(11) NOT NULL AUTO_INCREMENT,
  `FirstName` varchar(50) CHARACTER SET utf8mb4 NOT NULL,
  `LastName` varchar(50) CHARACTER SET utf8mb4 NOT NULL,
  `Suffix` varchar(6) DEFAULT NULL,
  `EmailAddress` varchar(100) CHARACTER SET utf8mb4 DEFAULT NULL,
  `IsPlantManager` tinyint(3) unsigned NOT NULL,
  `IsActive` tinyint(3) unsigned NOT NULL,
  PRIMARY KEY (`ContactId`)
) ;

`Site` (
  `SiteId` int(11) NOT NULL AUTO_INCREMENT,
  `SiteCode` varchar(10) CHARACTER SET utf8mb4 NOT NULL,
  `SiteName` varchar(255) CHARACTER SET utf8mb4 NOT NULL,
  `AddressId` int(11) NOT NULL,
  `BusinessId` int(11) DEFAULT NULL,
  `TotalUsers` int(11) DEFAULT NULL,
  `AdContainer` longtext,
  `SapLocation` varchar(100) CHARACTER SET utf8mb4 DEFAULT NULL,
  `Ldap` longtext,
  `SapCode` varchar(10) CHARACTER SET utf8mb4 DEFAULT NULL,
  `PrinterCode` varchar(6) CHARACTER SET utf8mb4 DEFAULT NULL,
  `ZoneId` int(11) DEFAULT NULL,
  PRIMARY KEY (`SiteId`),
  UNIQUE KEY `SiteCode_UNIQUE` (`SiteCode`),
  KEY `FK_Site_Address` (`AddressId`),
  KEY `FK_Site_BusinessGroup` (`BusinessId`),
  KEY `FK_Zone_Site_idx` (`ZoneId`),
  CONSTRAINT `FK_Site_Address` FOREIGN KEY (`AddressId`) REFERENCES `address` (`AddressId`) ON DELETE NO ACTION ON UPDATE CASCADE,
  CONSTRAINT `FK_Site_BusinessGroup` FOREIGN KEY (`BusinessId`) REFERENCES `businessgroup` (`BusinessId`) ON DELETE SET NULL ON UPDATE CASCADE,
  CONSTRAINT `FK_Zone_Site` FOREIGN KEY (`ZoneId`) REFERENCES `zone` (`ZoneId`) ON DELETE SET NULL ON UPDATE CASCADE
);

`SiteContact` (
  `ContactId` int(11) NOT NULL,
  `SiteId` int(11) NOT NULL,
  PRIMARY KEY (`ContactId`,`SiteId`),
  KEY `FK_Site_SiteContact_idx` (`SiteId`),
  CONSTRAINT `FK_Contact_SiteContact` FOREIGN KEY (`ContactId`) REFERENCES `contact` (`ContactId`) ON DELETE NO ACTION ON UPDATE CASCADE,
  CONSTRAINT `FK_Site_SiteContact` FOREIGN KEY (`SiteId`) REFERENCES `site` (`SiteId`) ON DELETE NO ACTION ON UPDATE CASCADE
);

 

Fluent Mapping:

var contactConfiguration = new MappingConfiguration<Contact>();
            contactConfiguration.MapType().WithDataAccessKind(DataAccessKind.ReadWrite).ToTable(tableName: "Contact");
            contactConfiguration.HasProperty(ct => ct.ContactId).IsIdentity(KeyGenerator.Autoinc);

            configurations.Add(contactConfiguration);

var siteContactConfiguration = new MappingConfiguration<SiteContact>();
            siteContactConfiguration.MapType().WithDataAccessKind(DataAccessKind.ReadWrite).ToTable(tableName: "SiteContact");
            siteContactConfiguration.HasProperty(sc => sc.ContactId).IsIdentity();
            siteContactConfiguration.HasProperty(sc => sc.SiteId).IsIdentity();

var siteConfiguration = new MappingConfiguration<Site>();
            siteConfiguration.MapType().WithDataAccessKind(DataAccessKind.ReadWrite).ToTable(tableName: "Site");
            siteConfiguration.HasProperty(s => s.SiteId).IsIdentity(KeyGenerator.Autoinc);

            siteConfiguration.HasAssociation(s => s.Address).WithLoadBehavior(LoadBehavior.Eager).WithOpposite(a => a.Site).HasConstraint((s, a) => s.AddressId == a.AddressId);
            siteConfiguration.HasAssociation(s => s.BusinessGroup).WithLoadBehavior(LoadBehavior.Lazy).WithOpposite(bg => bg.Sites).HasConstraint((s, bg) => s.BusinessId == bg.BusinessId);
            siteConfiguration.HasAssociation(s => s.Zone).WithLoadBehavior(LoadBehavior.Lazy).WithOpposite(z => z.Sites).HasConstraint((s, z) => s.ZoneId == z.ZoneId);
            configurations.Add(siteConfiguration);

            siteContactConfiguration.HasAssociation(sc => sc.Contact).WithLoadBehavior(LoadBehavior.Eager).WithOpposite(ct => ct.SiteContact).HasConstraint((sc, ct) => sc.ContactId == ct.ContactId).IsManaged();
            siteContactConfiguration.HasAssociation(sc => sc.Site).WithLoadBehavior(LoadBehavior.Eager).WithOpposite(s => s.SiteContacts).HasConstraint((sc, s) => sc.SiteId == s.SiteId).IsManaged();
            configurations.Add(siteContactConfiguration);

 

Error Message:

Additional information: The field 'siteContact' of class 'ItsdData.DAL.Contact' must use nested db-column extensions in a db-ref extension as the class 'ItsdData.DAL.SiteContact' has a composite primary key. --> FromMetadataContainer/namespace[ItsdData.DAL]/class[Contact]/field[siteContact]/db-column