Entity Framework 5.0 PostgreSQL (Npgsql) default connection factory

Question

I'm trying to get EF 5.0 code first working with PostgreSQL (Npgsql provider). I have Npgsql 2.0.12.1 installed via NuGet (referenced assembly is 2.0.12.0 though). I have Npgsql declared in app.config (both default connection factory and provider factory):

<entityFramework>   
    <defaultConnectionFactory type="Npgsql.NpgsqlFactory, Npgsql, Version=2.0.12.0, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7" />
 </entityFramework>
 <system.data>
        <DbProviderFactories>
          <add name="Npgsql Data Provider"
                invariant="Npgsql"
                description="Data Provider for PostgreSQL"
                support="FF"
                type="Npgsql.NpgsqlFactory, Npgsql, Version=2.0.12.0, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7"/>
        </DbProviderFactories>
 </system.data>

I have following test running successfully :

[Test]
public void DatabaseConnection_DatabaseFactoryTest()
{
    var factory = DbProviderFactories.GetFactory("Npgsql");
    var conn = factory.CreateConnection();
    conn.ConnectionString = _connectionString;
    var npg = (NpgsqlConnection)conn;
    var result = TestConnectionHelper(npg); // scalar select version(), nothing particular
    Assert.AreEqual(result, "PostgreSQL 9.2.2, compiled by Visual C++ build 1600, 64-bit");            
}

That means at least database instance is running and provider is configured successfully. Now what i want is to use custom database context inherited from DbContext which will be tied to same provider and initialized via connection string :

public class InventoryContext : DbContext
{
    public InventoryContext(string nameOrConnectionString) : base(nameOrConnectionString)
    {
    }
    // mappings and properties, cut for conciseness
}

Following test fails :

[Test]
public void DatabaseConnection_DatabaseContextTest()
{
    using (var ctx = new InventoryContext(_connectionString))
    {
        //var db = ctx.Database;
        ctx.InventoryObjects.Add(_inventoryObject); // exception here
        ctx.SaveChanges();
    }
}   

It says

Failed to set Database.DefaultConnectionFactory to an instance of the 'Npgsql.NpgsqlFactory, Npgsql, Version=2.0.12.0, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7' type as specified in the application configuration. See inner exception for details.

Inner exception is InvalidOperationException :

{"Constructor for type \"Npgsql.NpgsqlFactory\" is not found."}

I guess there is a problem with connection string (it does not contain Npgsql provider) :

"Server=127.0.0.1;Port=5432;User Id=postgres;Password=p4ssw0rd;Database=InventoryDatabase;";

What is the most elegant way to solve this problem programmatically? Just tried passing connectionString from app.config to context's constructor, it works.
edit
Uploaded test project to Dropbox - VS2012 solution, 10 mb

Solution

Dug deeper into the problem, found out that it is caused by that fact that Npgsql is referencing EntityFramework 4.4.0 assembly. Solved as follows :

1. Added EF Nuget package to test project (which is build against FW 4.5);
2. Manually added reference to EntityFramework.dll version 5 in Npgsql2010 project (Nuget adds 4.4.0 by default);
3. Changed assembly binding in Npgsql app.config to "EntityFramework, Version=5.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089";
4. Fixed described above "Constructor for type "Npgsql.NpgsqlFactory" is not found error by making constructor public;

5. Fixed following error "Unable cast NpgsqlFactory to IDbConnectionFactory" by implementing IDbConnectionFactory interface on NpgsqlFactory :

   using System.Data.Entity.Infrastructure;
   ...
   public sealed class NpgsqlFactory : DbProviderFactory, IServiceProvider, IDbConnectionFactory
   ...
   public DbConnection CreateConnection(string nameOrConnectionString)
   {
   return new NpgsqlConnection(nameOrConnectionString);
   }
   d

Now i'm experiencing "Error: 3F000: schema "dbo" doesn't exist" which is related to EF. I have mapping to PostgreSQL standard public schema in DbContext's OnModelCreating : modelBuilder.Entity().ToTable("TableName", "public") though. Looking forward to solution of this problem.

Comments

[Francisco Junior]

Great! I'll add the reported missing pieces right away: constructor visibility and interface implementation. Thanks for checking that.

[Francisco Junior]

I think I jumped too fast. When checking msdn documentation, I noticed that SqlClientFactory is one thing and SqlConnectionFactory is another. NpgsqlFactory is the equivalent to SqlClientFactory. In order to satisfy this problem, we need to create another class called NpgsqlConnectionFactory which will be tied to Entity Framework support. Sorry for that. I'll check how we will do that.

[Jammer]

I've given up on using EntityFramework with PostgreSQL and Npgsql these issues are fixed. No way am I going into production with this until it's more stable.

[Francisco Junior]

Hi all! I just committed a contribution which adds initial support for EF6. You can see more info in my post about it: fxjr.blogspot.com/2013/06/… Please, give it a try and let me know if it works for you.