Unable to determine the relationship represented by navigation property

Question

I'm getting a client-side error when trying to save an entity. 2 tables have a one-to-many and one-to-zero relationship at the same time and this is causing the following error:

Unable to determine the relationship represented by navigation property 'Group.LockedByUser' of type 'User'. Either manually configure the relationship, or ignore this property using the '[NotMapped]' attribute or by using 'EntityTypeBuilder.Ignore' in 'OnModelCreating

These are my current contexts:

User entity

public class User
{
    [Key]
    public int UserId { get; set; }
    public string Username { get; set; }
    public int GroupId { get; set; }

    public Group GroupThisUserBelongsTo { get; set; }
    public ICollection<Group> GroupsLockedByThisUser { get; set; }
    public ICollection<Config> Configs { get; set; }
}

Group entity

public class Group
{ 
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int GroupId { get; set; }
    public string GroupName { get; set; }
    public int? LockedByUserId { get; set; }

    public User LockedByUser { get; set; }
    public ICollection<User> Users { get; set; }
}

DbContext1 extract

modelBuilder.Entity<Group>(entity =>
        {
            entity.HasOne(d => d.LockedByUser)
                .WithMany(p => p.GroupsLockedByThisUser)
                .HasForeignKey(d => d.LockedByUserId);
        }

modelBuilder.Entity<User>(entity =>
        {
            entity.HasOne(d => d.GroupThisUserBelongsTo)
                .WithMany(p => p.Users)
                .HasForeignKey(d => d.GroupId)
                .OnDelete(DeleteBehavior.ClientSetNull);
        });

Config entity

public class Config
{
    [Key]
    public int ConfigId { get; set; }
    public int UserId { get; set; }
    public string Config { get; set; }

    public User User { get; set; }
}

DbContext2 extract

 modelBuilder.Entity<Config>(entity =>
        {
            entity.HasOne(d => d.User)
                .WithMany(p => p.Configs)
                .HasForeignKey(d => d.UserId);
        });

The piece of code generating the error is as follows:

var config = new Config {
            UserId = 123456,
            Config = "test"
        };

        _dbContext2.Config.Add(config);
        _dbContext2.SaveChanges();

I really don't understand why I get a client-side error when trying to save that entity. The error isn't even from the context from which I am trying to save.

Are my foreign keys set properly?

Group has many User - User has one Group (FK GroupId)
User locks zero or many Group (FK LockedByUserId)
Config has one User (FK UserId)

You've configured the Navigation Property User.Group on both relationships. Try renaming the Navigation Properties on user to "GroupThisUserBelongsTo" and "GroupsLockedByThisUser" to help you configure the navigation properties correctly. — David Browne - Microsoft
Thanks for your comment @DavidBrowne-Microsoft, I've edited my question with your advice. I have tried it and I still get the same error. I've tripled checked everything and I think I got the relationships right this time. — Raphael Laurent
maybe you need to remove this .WithMany(p => p.Users) and why don't you use normal virtual keyword to define relations. — Rudresha Parameshappa
Hey @RudreshaParameshappa, here is a link on virtual: stackoverflow.com/a/41881299/3768672. I don't need it in my case. Also I can't remove half of a relationship afaik. — Raphael Laurent

David Browne - Microsoft David Browne - Microsoft · Accepted Answer · 2018-05-01T21:45:32

Tried to repro the error. No repro:

using Microsoft.EntityFrameworkCore;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.ComponentModel.DataAnnotations.Schema;
using System.ComponentModel.DataAnnotations;
//using Microsoft.Samples.EFLogging;
using System.Data.SqlClient;
using System.Xml.Linq;
using System.Threading.Tasks;

namespace EFCore2Test
{

    public class User
    {
        [Key]
        [DatabaseGenerated( DatabaseGeneratedOption.None)]
        public int UserId { get; set; }
        public string Username { get; set; }
        public int GroupId { get; set; }

        public Group GroupThisUserBelongsTo { get; set; }
        public ICollection<Group> GroupsLockedByThisUser { get; set; }

        public ICollection<Config> Configs { get; set; }
    }
    public class Group
    {
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int GroupId { get; set; }
        public string GroupName { get; set; }
        public int? LockedByUserId { get; set; }

        public User LockedByUser { get; set; }
        public ICollection<User> Users { get; set; }
    }

    public class Config
    {
        [Key]
        public int ConfigId { get; set; }
        public int UserId { get; set; }
        public string ConfigName { get; set; }

        public User User { get; set; }
    }

    public class Db : DbContext
    {
        public DbSet<User> Users { get; set; }
        public DbSet<Group> Groups { get; set; }

        public DbSet<Config> Configs { get; set; }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Group>()
                .HasOne(d => d.LockedByUser)
                .WithMany(p => p.GroupsLockedByThisUser)
                .HasForeignKey(d => d.LockedByUserId);            

            modelBuilder.Entity<User>()
                .HasOne(d => d.GroupThisUserBelongsTo)
                .WithMany(p => p.Users)
                .HasForeignKey(d => d.GroupId)
                .OnDelete(DeleteBehavior.ClientSetNull);

            modelBuilder.Entity<Config>()
                .HasOne(d => d.User)
                .WithMany(p => p.Configs)
                .HasForeignKey(d => d.UserId);            

            base.OnModelCreating(modelBuilder);
        }
        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseSqlServer("Server=(local);Database=EFCoreTest;Trusted_Connection=True;MultipleActiveResultSets=true");
            base.OnConfiguring(optionsBuilder);
        }
    }

    class Program
    {   

        static void Main(string[] args)
        {            
            using (var db = new Db())
            {
                db.Database.EnsureDeleted();

                db.Database.EnsureCreated();
                //db.ConfigureLogging(s => Console.WriteLine(s));

                var g = new Group()
                {
                    GroupName = "G"
                };

                var u = new User()
                {
                    UserId = 123456,
                    GroupThisUserBelongsTo = g
                };                

                db.Users.Add(u);
                db.SaveChanges();

                g.LockedByUser = u;
                db.SaveChanges();

            }

            using (var db = new Db())
            {
                var config = new Config
                {
                    UserId = 123456,
                    ConfigName = "test"
                };

                db.Configs.Add(config);
                db.SaveChanges();
            }


            Console.WriteLine("Hit any key to exit");
            Console.ReadKey();
        }
    }
}

Unable to determine the relationship represented by navigation property

2 Answers