Cascading Referential Integrity Constraints for many to many relationships in EF Core

I'm using EF Core 3.1.5 with Asp.Net Core 3.1. When I'm trying to Add-Migration I get next error:

Microsoft.Data.SqlClient.SqlException (0x80131904): Introducing FOREIGN KEY constraint 'FK_PhotoDevice_Device_DeviceId' on table 'PhotoDevice' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.

I have next entities and configuration:

public class User {
   [Key]
   public long Id { get; set; }
   // Fields
   public IEnumerable<Device> Devices { get; set; }
   public IEnumerable<Photo> Photos { get; set; }
}

public class Photo {
   [Key]
   public long Id { get; set; }
   // Fields
   [ForeignKey("User")]
   public long UserRef { get; set; }
   public User User { get; set; }
   public IEnumerable<PhotoDevice> PhotoDevices { get; set; }
}

public class Device {
   [Key]
   public long Id { get; set; }
   // Fields
   [ForeignKey("User")]
   public long UserRef { get; set; }
   public User User { get; set; }
   public IEnumerable<PhotoDevice> PhotoDevices { get; set; }
}

public class PhotoDevice {
{
   public long? PhotoRef { get; set; }
   public Photo Photo { get; set; }

   public long? DeviceRef { get; set; }
   public Device Device { get; set; }
}

public class AppDbContext : DbContext
{
   public DbSet<User> Users { get; set; }
   public DbSet<Photo> Photos { get; set; }
   public DbSet<Device> Devices { get; set; }
   public DbSet<PhotoDevice> PhotoDevices { get; set; }
   public AppDbContext(DbContextOptions<AppDbContext> options)
   : base(options)
   {
      Database.Migrate();
   }

   protected override void OnModelCreating(ModelBuilder builder)
   {
      builder.Entity<Photo>()
         .HasOne(photo => photo.User)
         .WithMany(user => user.Photos);

      builder.Entity<Device>()
         .HasOne(device => device.User)
         .WithMany(user => user.Devices);

      builder.Entity<PhotoDevice>()
         .HasKey(bc => new { bc.PhotoRef, bc.DeviceRef });
      builder.Entity<PhotoDevice>()
         .HasOne(bc => bc.Photo)
         .WithMany(b => b.PhotoDevices)
         .HasForeignKey(bc => bc.PhotoRef);
      builder.Entity<PhotoDevice>()
         .HasOne(bc => bc.Device)
         .WithMany(c => c.PhotoDevices)
         .HasForeignKey(bc => bc.DeviceRef);
   }
}

I found that problem is related to not uniqueness of cascading connections. But now I'm confused. Because I think that this structure is necessary and I don't want to drop any FK. How can I fix the problem If I need next logic:

• When User deleted all devices and photos related to the user are also removed
• When Device or Photo deleted all PhotoDevice records related to the deleted entity are removed too

What lauxjpn said is correct, but please note that when you add .OnDelete(DeleteBehavior.Restrict); to your context after that, please remember to delete all your previous migrations, otherwise it will still report an error.