Net Core: No implicit reference conversion from 'Entities' to 'IEntity'

Question

Net Core: No implicit reference conversion from 'Entities' to 'IEntity'

.net-core asp.net-core c# entity-framework-core

Question

I have Generic Repository below. I also have Entity framework class called Queue which maps to database. The goal is use implement the repository in API for QueueTable.

Base Repository:

public class BaseRepository<T, TPrimaryKey> : IRepository<T, TPrimaryKey> where T : class, IEntity<TPrimaryKey>
{
    protected readonly DbContext _context;
    protected virtual DbSet<T> Table { get; }
    protected IQueryable<T> All => Table.AsNoTracking();
    public BaseRepository(DbContext context)
    {
        _context = context;
        Table = _context.Set<T>();
    }
    public IQueryable<T> GetAll()
    {
        return All;
    }
    public async Task DeleteAsync(T entity)
    {
        await Task.FromResult(_context.Set<T>().Remove(entity));
    }

Generic Repository:

public interface IRepository<T, TPrimaryKey> where T : IEntity<TPrimaryKey>
{    
    IQueryable<T> GetAll();
    DeleteAsync(T entity);

............

Model

public class Queue
{
    public Queue()
    {
        QueueHistory = new HashSet<QueueHistory>();
    }
    public int QueueId { get; set; }
    public int? QueueStatusId { get; set; }
    public int? OriginalDepartmentId { get; set; }
    public int? CreatedByUserId { get; set; }
    public int? ObjectType { get; set; }
    public int? ObjectId { get; set; }

IEntity:

public interface IEntity<TPrimaryKey>
{
    [NotMapped]
    TPrimaryKey Id { get; set; }
}

public interface IEntity : IEntity<int>
{
}

API:

In trying to declare the Repository in API Controller, it states this

public class QueuesController : ControllerBase
{
    private readonly AssessmentContext _context;

    public Queue queue = new Queue();
    public BaseRepository<Queue,QueueId> queueRepository;

Error:

The type .Entities.Queue' cannot be used as type parameter 'T' in the generic type or method 'BaseRepository<T, TPrimaryKey>'. There is no implicit reference conversion from 'DomainModels.Entities.Queue' to 'Interfaces.IEntity<QueueId>'.

Trying to convert creates issue.

How would I resolve this error?

jerrythomas38

View more on Stack Overflow

arynaq · Accepted Answer · 7/26/2019 10:03:10 PM

I think the issue you are having is understanding how type constraints work, a rough skeleton (that makes the compiler happy) of what you are looking for is something like this, I leave the actual implementation to you :)

Note that I remade some of the classes/interfaces, you can use the IEntity you have yourself from EF, eg:

public interface IEntity<T>
{
    T Id {get;set;}
}

public interface IRepository<T, TPrimaryKey> where T: IEntity<TPrimaryKey>{}

public class BaseRepository<T, TPrimaryKey> : IRepository<T, TPrimaryKey> where T: class, IEntity<TPrimaryKey>{}

public class Queue : IEntity<int>
{
    public int Id {get;set;}
}

public class QueueRepository : BaseRepository<Queue, int>
{
}

public class QueueController
{
    //Not a good idea
    private readonly BaseRepository<Queue, int> queueRepository;

    //Better
    private readonly QueueRepository _queueRepository;
}

Net Core: No implicit reference conversion from 'Entities' to 'IEntity'

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