Many-to-many relationship using Sqlite-net extensions, getting NotSupportedException: Don't know about System.Collections.Generic.List

Question

I have a new Xamarin Forms application where I'm trying to make use of Sqlite-net and Sqlite-net extensions for an ORM. I've followed This guide to create the n:n. Here are my two objects, as well as their intermediate object:

Nation

using Sqlite;
using SQLiteNetExtensions.Attributes;
using System.Collections.Generic;

namespace MyNamespace.Models
{    
    public class Nation
    {
        [PrimaryKey, AutoIncrement]
        public int Id { get; set; }

        public string Name { get; set; }

        public string Adjective { get; set; }

        public double Frequency { get; set; }

        [ManyToMany(typeof(NationFirstName))]
        public List<FirstName> FirstNames { get; set; }
    }
}

FirstName

using SQLite;
using SQLiteNetExtensions.Attributes;
using System.Collections.Generic;

namespace MyNamespace.Models
{
    public class FirstName
    {
        [PrimaryKey, AutoIncrement]
        public int Id { get; set; }

        public string Name { get; set; }

        [ManyToMany(typeof(NationFirstName))]
        public List<Nation> Nations { get; set; }
    }
}

NationFirstName

using SQLite;
using SQLiteNetExtensions.Attributes;

namespace OffseasonGM.Models
{
    public class NationFirstName
    {
        [ForeignKey(typeof(Nation))]
        public int NationId { get; set; }

        [ForeignKey(typeof(FirstName))]
        public int FirstNameId { get; set; }
    }
}

And so, in my app's starting point, App.xaml.cs, I try to first create the NationFirstNameRepository, which works well. And next, I try to create the NationRepository, where I get an exception in the constructor. On the CreateTable() line:

[ERROR] FATAL UNHANDLED EXCEPTION: System.NotSupportedException: Don't know about System.Collections.Generic.List`1[OffseasonGM.Models.FirstName]

NationRepository.cs

using MyNamespace.Models;
using SQLite;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Threading.Tasks;

namespace MyNamespace.Assets.Repositories
{
    public class NationReposistory
    {
        SQLiteConnection connection;

        public NationReposistory(string dbPath)
        {
            connection = new SQLiteConnection(dbPath);
            var entriesCreatedCount = connection.CreateTable<Nation>();
            if (entriesCreatedCount < 1)
            {
                SeedNations();
            }
        }

        public void AddNewNation(string name, string adjective, double frequency)
        {
            try
            {
                connection.Insert(new Nation { Name = name, Adjective = adjective, Frequency = frequency });
            }
            catch (Exception e)
            {
                //TODO: Error handling.
            }
        }

        public List<Nation> GetAllNations()
        {
            return connection.Table<Nation>().ToList();
        }

        private void SeedNations()
        {
            var assembly = typeof(MainPage).GetTypeInfo().Assembly;
            var stream = assembly.GetManifestResourceStream("MyNamespace.Nations.txt");
            using (var reader = new StreamReader(stream))
            {
                var line = reader.ReadLine().Split('|');
                var name = line[0];
                var adjective = line[1];
                var frequency = double.Parse(line[2]);
                AddNewNation(name, adjective, frequency);
            }
        }
    }
}

Am I doing something out of order, or altogether forgetting something? Very thankful for any advice.

score 0 · Answer 1 · answered Mar 10 '18 at 14:28

Same error here. I uninstall all nugets wich contains PCL, delete bin and obj folders, clean solution, add SQLiteNetExtensions 1.3.0 and SQLite.Net-PCL 3.1.1 nugets, clean again and rebuild. Work for me, i imagine there is some incompatibility between the newer versions of these packages.

Hope this helps!

Many-to-many relationship using Sqlite-net extensions, getting NotSupportedException: Don't know about System.Collections.Generic.List

1 Answers1