mapping
Class Mapping Error: ‘T’ must be a non-abstract type with a public parameterless constructor
The problem is that you’re trying to use the T from SqlReaderBase as the type argument for MapperBase – but you don’t have any constraints on that T. Try changing your SqlReaderBase declaration to this: public abstract class SqlReaderBase<T> : ConnectionProvider where T : new() Here’s a shorter example which demonstrates the same issue: class … Read more
Navigation Property without Declaring Foreign Key
I believe, it is not possible to define the relationship only with data attributes. The problem is that EF’s mapping conventions assume that Creator and Modifier are the two ends of one and the same relationship but cannot determine what the principal and what the dependent of this association is. As far as I can … Read more
Entity Framework 4.1 InverseProperty Attribute and ForeignKey
It is theoretically correct but SQL server (not Entity framework) doesn’t like it because your model allows single employee to be a member of both First and Second team. If the Team is deleted this will cause multiple delete paths to the same Employee entity. This cannot be used together with cascade deletes which are … Read more
JPA Map mapping
Although answer given by Subhendu Mahanta is correct. But @CollectionOfElements is deprecated. You can use @ElementCollection instead: @ElementCollection @JoinTable(name=”ATTRIBUTE_VALUE_RANGE”, joinColumns=@JoinColumn(name=”ID”)) @MapKeyColumn (name=”RANGE_ID”) @Column(name=”VALUE”) private Map<String, String> attributeValueRange = new HashMap<String, String>(); There is no need to create a separate Entity class for the Map field. It will be done automatically.
Mapping a NumPy array in place
It’s only worth trying to do this in-place if you are under significant space constraints. If that’s the case, it is possible to speed up your code a little bit by iterating over a flattened view of the array. Since reshape returns a new view when possible, the data itself isn’t copied (unless the original … Read more
Using AutoMapper to unflatten a DTO
This also seems to work for me: Mapper.CreateMap<PersonDto, Address>(); Mapper.CreateMap<PersonDto, Person>() .ForMember(dest => dest.Address, opt => opt.MapFrom( src => src ))); Basically, create a mapping from the dto to both objects, and then use it as the source for the child object.
How to introduce multi-column constraint with JPA annotations?
You can declare unique constraints using the @Table(uniqueConstraints = …) annotation in your entity class, i.e. @Entity @Table(uniqueConstraints={ @UniqueConstraint(columnNames = {“productId”, “serial”}) }) public class InventoryItem { … } Note that this does not magically create the unique constraint in the database, you still need a DDL for it to be created. But seems like … Read more
Hibernate – Foreign keys instead of Entities
Yes, you can do that. You just need to make it clear for hibernate which one is the mapping that it’s supposed to maintain, like so: @Column(name=”message_key”, updatable=false, insertable=false) private Long message_fk;
Entity framework code-first null foreign key
You must make your foreign key nullable: public class User { public int Id { get; set; } public int? CountryId { get; set; } public virtual Country Country { get; set; } }