entity framework - EF Core Fluent API statement as Data Annotation

Question

Can I write this with data annotations in EF Core?

modelBuilder.Entity<DiagramComponent>()
                .HasOne(c => c.Compressor)
                .WithMany(c => c.Components);

question from:https://stackoverflow.com/questions/65882725/ef-core-fluent-api-statement-as-data-annotation

Answer 1

You will have to create one more class:

public class DiagramComponentComponent
    {
        public int DiagramComponentId { get; set; }
        public int ComponentId { get; set; }

        [ForeignKey(nameof(DiagramComponentId))]
        public virtual DiagramComponent DiagramComponent { get; set; }

        [ForeignKey(nameof(ComponentId))]
        public virtual Component Component { get; set; }
    }

and add attributes to existing classes:

public class DiagramComponent
    {
        public int CompressorId { get; set; }

        [ForeignKey(nameof(CompressorId))]
        [InverseProperty("DiagramComponents")]
        public virtual Compressor Compressor { get; set; }

[InverseProperty(nameof(DiagramComponentComponent.DiagramComponent))]
public virtual ICollection<DiagramComponentComponent> DiagramComponentComponents { get; set; }
    }
    public class Compressor
    {
        [InverseProperty(nameof(DiagramComponent.Compressor))]
        public virtual ICollection<DiagramComponent> DiagramComponents { get; set; }

    }
    public class Component
    {
[InverseProperty(nameof(DiagramComponentComponent.Component))]
public virtual ICollection<DiagramComponentComponent> DiagramComponentComponents { get; set; }

    }

and add to dbcontext:

modelBuilder.Entity<DiagramComponentComponent>(entity =>
            {
                entity.HasOne(d => d.DiagramComponent )
                    .WithMany()
                    .HasForeignKey(d => d.DiagramComponentId )
                    .OnDelete(DeleteBehavior.ClientSetNull)
          .HasConstraintName("FK_DiagramComponentComponent_Component_Diagram");

                entity.HasOne(d => d.Component)
                    .WithMany()
                    .HasForeignKey(d => d.ComponentId )
                    .OnDelete(DeleteBehavior.ClientSetNull)
                    .HasConstraintName("FK_DiagramComponentComponent_Component");
            });