Linq on DbSet throws missing method

Using linq operations .single() and .where() seem to fail :

System.MissingMethodException: 'Method not found: 'System.Reflection.MethodInfo 

Version: Npgsql.EntityFrameworkCore.PostgreSQL Version=“2.2.0-preview1”

using Microsoft.EntityFrameworkCore;
using System;
using System.Collections.Generic;
using System.Linq;

namespace ConsoleApp1
{
    public class Blog
    {
        public Guid Id { get; set; }
    }
    public class BloggingContext : DbContext
    {
        private string connectionString = $"Host=localhost;Port=15432;Database=testDB;Username=postgres;Password=postgres";
        public BloggingContext()
        {
            Database.EnsureCreated();
        }
        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder
                .UseLazyLoadingProxies()
                .UseNpgsql(connectionString);
            base.OnConfiguring(optionsBuilder);
        }
        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Blog>();
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            using (var db = new BloggingContext())
            {
                Blog blog = new Blog();
                db.Set<Blog>().Add(blog);
                Blog contextBlog = null;
                contextBlog = db.Set<Blog>().Find(blog.Id); //OK
                contextBlog = db.Set<Blog>().SingleOrDefault(p => p.Id == blog.Id); //NOK
                List<Blog> test = db.Set<Blog>().Where(p => p.Id == blog.Id).ToList(); //NOK
            }
        }
    }
}

csproj

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp2.0</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.EntityFrameworkCore.Proxies" Version="2.2.0-preview3-35497" />
    <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="2.2.0-preview1" />
  </ItemGroup>

</Project>

[jornvl90]

Its my understanding that this is the expected behavior. Further, I’m pretty sure that behavior is defined in general for EF Core (i.e. the PostgreSQL provider isn’t driving it).

Thinking through it, you’ve basically got a partially completed operation happening here, and if those were to work, but then you disposed without saving, later queries would fail in a confusing way. That feels more inconsistent than the current behavior.

@roji Could you weigh in here?

It seems to be an EF decision indeed (https://stackoverflow.com/questions/699648/entity-framework-re-finding-objects-recently-added-to-context) But feels weird that .Find(id) does return the unsaved object and the others do not…

[austindrenski]

Great to hear, thanks for linking to that answer.

I’m going to close this since the initial issue is resolved. But feel free to continue posting if you have other questions or issues related to using the PostgreSQL provider.