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Q&A How to refer to the same class twice from one Entity Framework entity?

I tried to replicate your case and the only workable solution I could find is to use OnModelCreating configuration (fluent style) instead of attributes: public class Contestant { public int Id...

posted 2y ago by Alexei‭ · edited 2y ago by Alexei‭

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#2: Post edited by

Alexei‭ · 2022-10-12T17:58:19Z (about 2 years ago)
added a side note

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I tried to replicate your case and the only workable solution I could find is to use OnModelCreating configuration (fluent style) instead of attributes:
```c#
public class Contestant
{
public int Id { get; set; }
public int AvatarID { get; set; }
public virtual Picture? Avatar { get; set; }
public virtual ICollection<Picture>? Pictures { get; set; }
}
public class Picture
{
public int Id { get; set; }
public int ContestantID { get; set; }
public virtual Contestant? Contestant { get; set; }
public virtual Contestant? ContestantInverse { get; set; }
}
modelBuilder.Entity<Contestant>()
.HasOne(u => u.Avatar)
.WithOne(r => r.Contestant)
.HasForeignKey<Contestant>(u => u.AvatarID)
.HasConstraintName("FK_Contestant_Avatar")
.OnDelete(DeleteBehavior.Restrict);
modelBuilder.Entity<Picture>()
.HasOne(d => d.ContestantInverse)
.WithMany(p => p.Pictures)
.HasConstraintName("FK_Picture_Contestant")
.OnDelete(DeleteBehavior.Restrict);
```
~~The `Picture` needs two navigation properties related to `Contestant` since it has two relations with it (1:1 and n:1).~~

I tried to replicate your case and the only workable solution I could find is to use OnModelCreating configuration (fluent style) instead of attributes:
```c#
public class Contestant
{
public int Id { get; set; }
public int AvatarID { get; set; }
public virtual Picture? Avatar { get; set; }
public virtual ICollection<Picture>? Pictures { get; set; }
}
public class Picture
{
public int Id { get; set; }
public int ContestantID { get; set; }
public virtual Contestant? Contestant { get; set; }
public virtual Contestant? ContestantInverse { get; set; }
}
modelBuilder.Entity<Contestant>()
.HasOne(u => u.Avatar)
.WithOne(r => r.Contestant)
.HasForeignKey<Contestant>(u => u.AvatarID)
.HasConstraintName("FK_Contestant_Avatar")
.OnDelete(DeleteBehavior.Restrict);
modelBuilder.Entity<Picture>()
.HasOne(d => d.ContestantInverse)
.WithMany(p => p.Pictures)
.HasConstraintName("FK_Picture_Contestant")
.OnDelete(DeleteBehavior.Restrict);
```
The `Picture` needs two navigation properties related to `Contestant` since it has two relations with it (1:1 and n:1).
As a side note, while liking the attributes more, I decided to use the fluent syntax only because some configurations are not supported by the attributes (e.g. index on 2+ properties), and having the configuration split in two can lead to confusion.

#1: Initial revision by

Alexei‭ · 2022-10-12T12:06:30Z (about 2 years ago)

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I tried to replicate your case and the only workable solution I could find is to use OnModelCreating configuration (fluent style) instead of attributes:

```c#
public class Contestant 
{
	public int Id { get; set; }

	public int AvatarID { get; set; }

	public virtual Picture? Avatar { get; set; }

	public virtual ICollection<Picture>? Pictures { get; set; }
}


public class Picture
{
	public int Id { get; set; }

	public int ContestantID { get; set; }

	public virtual Contestant? Contestant { get; set; }

	public virtual Contestant? ContestantInverse { get; set; }
}


modelBuilder.Entity<Contestant>()
	.HasOne(u => u.Avatar)
	.WithOne(r => r.Contestant)
	.HasForeignKey<Contestant>(u => u.AvatarID)
	.HasConstraintName("FK_Contestant_Avatar")
	.OnDelete(DeleteBehavior.Restrict);

modelBuilder.Entity<Picture>()
	.HasOne(d => d.ContestantInverse)
	.WithMany(p => p.Pictures)
	.HasConstraintName("FK_Picture_Contestant")
	.OnDelete(DeleteBehavior.Restrict);
```

The `Picture` needs two navigation properties related to `Contestant` since it has two relations with it (1:1 and n:1).

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