C# Entity Framework Core .Include() issue

Question

I'm having a problem with the entity framework's "Include()" function

Framework used: .NET Core 3.1 with Entity Framework Core 3.1.5

These are my entities

public class EntityA { [Key] [DatabaseGenerated(DatabaseGeneratedOption.Identity)] public int Id { get; set; } [Required] [Index(IsUnique = true)] public int EntityBId { get; set; } [ForeignKey("EntityBId")] public EntityB EntityB { get; set; } [DefaultValue(false)] public bool IsConfirmed { get; set; } } public class EntityB { [Key] [DatabaseGenerated(DatabaseGeneratedOption.Identity)] public int Id { get; set; } [Required] public string Title { get; set; } public string Description { get; set; } }

so I launch this query:

public ICollection<EntityA> GetAll(string contextName) { DbContext context = GetContext(contextName); ICollection<EntityA> collection = context.EntityAs .Include(j => j.EntityB) .Where(x => x.IsConfirmed) .ToList(); return collection; } private DbContext GetContext(string contextName) { string contextDbConnectionString = _secretsRepository.GetDbConnectionString(contextName); DbContextOptionsBuilder<DbContext> optionsBuilder = new DbContextOptionsBuilder<DbContext>(); optionsBuilder.UseSqlServer(contextDbConnectionString); return new DbContext(optionsBuilder.Options); }

the result of the query is as follows:

{ Id: 5 IsConfirmed: true EntityB: null EntityBId: 72 }

what I don't understand is why the "Include(j => j.EntityB)" does not return the EntityB field correctly valued

Try marking EntityB as virtual, so public virtual EntitiyB EntityB {get; set} — MindSwipe
– MindSwipe, Commented Jul 3, 2020 at 11:13
Please check the generated SQL to start with. Does it include the EntityB? — TomTom
– TomTom, Commented Jul 3, 2020 at 11:15
@TomTom I had already looked at it but the result of the generated query is this: SELECT [p].[Id], [p].[IsConfirmed], [p].[EntityBId] FROM [EntityAs] AS [p] HERE [p].[IsConfirmed] = CAST(1 AS bit) — Andrea Rosario Nicosia
– Andrea Rosario Nicosia, Commented Jul 3, 2020 at 11:22
Ok, so EfCore is not generating the SQL.Your DbContext is NOT registering the metadata properly, so relationships are never parsed. Look up how to configure the DbContext properly. — TomTom
– TomTom, Commented Jul 3, 2020 at 11:32

Durga Prasad · Accepted Answer · 2020-07-04 19:06:18Z

When I tried to build a data model with the entities provided in question, I encountered a compilation error at Index attribute.

[Required] [Index(IsUnique = true)] public int EntityBId { get; set; }

Turns out entity framework 6 libraries used to have that attribute, but the question talks about entity framework core. So I just removed the Index attribute and moved it to OnModelCreating method to mimic similar behavior.

protected override void OnModelCreating(ModelBuilder modelBuilder) { modelBuilder.Entity<EntityA>().HasIndex(u => u.EntityBId).IsUnique(); }

With that in place,I applied code first approach to generate the db and ran the program. Upon execution, ef core generated proper query:

SELECT [e].[Id], [e].[EntityBId], [e].[IsConfirmed], [e0].[Id], [e0].[Description], [e0].[Title] FROM [EntityAs] AS [e] INNER JOIN [EntityBs] AS [e0] ON [e].[EntityBId] = [e0].[Id] WHERE [e].[IsConfirmed] = CAST(1 AS bit)

Hope it helps in resolving your problem.

Thanks, this solved my problem, my problem was due to the entity framework 6 library with entity framework core library

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