ef core .Include().Contains() null reference exception

Question

I have my models setup like this...

public class Model1 : IEquatable<Model1>
{
    public int Model1Id { get; set; }
    public string Name1 { get; set; }
    public Model2 Model2 { get; set; }
    public int Model2Id { get; set; }

    public bool Equals(Model1 other)
    {
        return this.Model2.Equals(other.Model2)
            && this.Name1 == other.Name1;
    }
}

public class Model2 : IEquatable<Model2>
{
    public int Model2Id { get; set; }
    public string Name2 { get; set; }

    public bool Equals(Model2 other)
    {
        return this.Name2 == other.Name2;
    }
}

public class ModelContext : DbContext
{
    public DbSet<Model1> Model1 { get; set; }
    public DbSet<Model2> Model2 { get; set; }
    public ModelContext(DbContextOptions<ModelContext> options) : base(options) { }
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Model1>(b =>
        {
            b.HasOne(m1 => m1.Model2).WithMany().HasForeignKey(m1 => m1.Model2Id);
        });
    }
}

then I get a null reference exception when I do this...

static void Main(string[] args)
{
    var myModel1 = new Model1
    {
        Name1 = "myName1",
        Model2 = new Model2
        {
            Name2 = "myName2"
        }
    };
    var connection = new SqliteConnection("DataSource=:memory:");
    connection.Open();
    try
    {
        var options = new DbContextOptionsBuilder<ModelContext>()
            .UseSqlite(connection)
            .Options;

        //create database
        using(var ctx = new ModelContext(options))
        {
            ctx.Database.EnsureCreated();
        }

        //add model objects
        using (var ctx = new ModelContext(options))
        {
            ctx.Database.EnsureCreated();
            ctx.Model1.Add(myModel1);
            ctx.SaveChanges();
        }

        //check if exists
        using(var ctx = new ModelContext(options))
        {
            //exception here
            bool isExists = ctx.Model1.Include(m1 => m1.Model2).Contains(myModel1); 
            Console.WriteLine(isExists);
        }
    }
    finally
    {
        connection.Close();
    }

    Console.ReadKey();
}

I'm expeting the Model2 instance of my m1 to be populated when I call the Include but it is still null.

but If I add AsEnumerable() to my query like..

ctx.Model1.Include(m1 => m1.Model2).AsEnumerable().Contains(model1);

then everything works fine.

EDIT:

my question is... why do I need to call AsEnumerable()? I was expecting it to work without calling AsEnumerable()..

What are you even trying to do that makes no sense, do you want to check if the list contains something or do you want the full list — johnny 5, Jul 12 '17 at 21:21
Implementing `IEquatable` in mutable reference types but not overriding `Object.Equals` is like [playing Russian Roulette with 5 chambers loaded](https://stackoverflow.com/questions/3191969/). — Dour High Arch, Jul 12 '17 at 21:31
@PaoloGo - Could you please add enough code to your question so that I can copy, paste, and run you code that would be excellent? I think I have the answer for you but I want to test it first. I'm looking for a [mcve]. — Enigmativity, Jul 12 '17 at 23:23
@PaoloGo - I can't run a SQLite connection. I need to run your code. Can you remove the SQLite code and make it runable - just `new` up some of the variables and then show the issue you're having? — Enigmativity, Jul 13 '17 at 02:27

johnny 5 · Answer 1 · 2017-07-12T21:36:51.747

2

The difference is one is an entityframe work call the other is linq to objects Entity Framework Does not understand contains for a CLR Object

public void AddIfNotExists(Model1 model1)
{

    //No Need for the include this is executed in sql,  assuming the model 2 
    //property has already been included in your model1 this should work fine
    if(false == _context.Model1.Any(x => x.Name1 == model1.Name1 
                        && x.Model2.Name2 == model1.Model2.Name2))
    {
        _context.Model1.Add(model1);
    }
}

I made this based off of your logic, but chances are you really just want to check if model1.id is the the model1 set. But I have no Idea what your architecture is doing so this is what you probably want

edited Jul 12 '17 at 21:36

answered Jul 12 '17 at 21:24

johnny 5

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I updated my question to show that I'm trying to make a method AddIfNotExists. a – Jan Paolo Go Jul 12 '17 at 21:27
@PaoloGo did this work? If so can you mark as correct – johnny 5 Jul 12 '17 at 21:56

ef core .Include().Contains() null reference exception

1 Answers1