Dapper多映射错误

我正在努力让多映射在小巧玲珑中工作。

这是我的代码：

var contactDictionary = new Dictionary<Guid, Contact>();

IEnumerable<Contact> contacts = connection.Query<Contact, Activity, Contact>(
        @"SELECT ContactId, Title, FirstName, Surname, 
            AddressType.Type AS AddressType, Address.AddressLine1, Address.AddressLine2, Address.AddressLine3, Address.Town, Address.County, Address.Country, Address.Postcode,
            EmailAddressType.Type AS EmailAddressType, EmailAddress.Email AS EmailAddress,
            PhoneNumberType.Type As PhoneNumberType, PhoneNumber.Number AS PhoneNumber,
            Direction.Type AS Direction, Activity.Summary, Activity.DateCompleted
        FROM Contact
            LEFT JOIN Address ON Contact.ContactPK = Address.ContactPK
                LEFT JOIN AddressType ON Address.AddressTypePK = AddressType.AddressTypePK
            LEFT JOIN EmailAddress ON Contact.ContactPK = EmailAddress.ContactPK
                LEFT JOIN EmailAddressType ON EmailAddress.EmailAddressTypePK = EmailAddressType.EmailAddressTypePK
            LEFT JOIN PhoneNumber ON Contact.ContactPK = PhoneNumber.ContactPK
                LEFT JOIN PhoneNumberType ON PhoneNumber.PhoneNumberTypePK = PhoneNumberType.PhoneNumberTypePK
            LEFT JOIN Activity ON Contact.ContactPK = Activity.ContactPK
                LEFT JOIN Direction ON Activity.DirectionPK = Direction.DirectionPK
        WHERE Contact.ContactId = @ContactId
            AND Address.IsPrimary = 1 AND EmailAddress.IsPrimary = 1 AND PhoneNumber.IsPrimary = 1",
        param:new { ContactId = contactId },
        map:(c, a) =>
        {
            Contact contactEntry;

            if (!contactDictionary.TryGetValue(c.ContactId, out contactEntry))
            {
                contactEntry = c;
                contactEntry.Activities = new List<Activity>();
                contactDictionary.Add(contactEntry.ContactId, contactEntry);
            }

            contactEntry.Activities.Add(a);
            return contactEntry;
        },
        splitOn: "ContactId")
        .Distinct()
        .ToList();    

以下是在SSMS中运行时SQL的结果：

这是我在代码执行时得到的错误： 当使用多映射API时，如果你有除Id参数名以外的密钥，请确保设置splitOn参数：splitOn

我真的很困惑，因为我以为我已经指定了splitOn参数？

任何帮助，将不胜感激。