CODEWITHSUNDEEP
asp.net-mvcentity-frameworkmononpgsql
nixdaemon
nixdaemon

Reputation: 121

Mono 4.5 profile, entity framework Npgsql - NpgsqlSystem.InvalidCastException Cannot cast from source type to destination type

I have getting "System.InvalidCastException Cannot cast from source type to destination type." when trying to access the database from asp.net mvc3 using mono 4.5 profile and postgres at the backend.

Here is what my code looks like:

public class User
{
    public int Id { get; set; }
    public string Username { get; set; }
    public string PasswordHash { get; set; }
    public string PasswordSalt { get; set; }    
} // class

AppContext:

using System;
using System.Data.Entity;
using Npgsql;
using NpgsqlTypes;

namespace Web
{
public class AppContext : DbContext
{
    public DbSet<User> Users { get; set; }

    protected override void OnModelCreating (DbModelBuilder modelBuilder)
    {
        base.OnModelCreating (modelBuilder);
    }   
} // class
} // namespace

Database schema (dbo)

CREATE TABLE dbo."Users"
(
"Id" integer NOT NULL DEFAULT nextval('dbo."Users_Id_seq"'::regclass),
"Username" character varying(50) NOT NULL,
"PasswordHash" character varying(255) NOT NULL,
"PasswordSalt" character varying(128) NOT NULL,
CONSTRAINT pk_users_id PRIMARY KEY ("Id")
)

public class HomeController : Controller
{
    public ActionResult Index ()
    {
        var db = new AppContext();
        var users = db.Users.Find(1);
        ViewData ["Message"] = "Welcome to ASP.NET MVC on Mono!";
        return View ();
    }
}

error i am getting is:

System.InvalidCastException

Cannot cast from source type to destination type.

Description: HTTP 500.Error processing request.
Details: Non-web exception. Exception origin (name of application or object): Npgsql.
Exception stack trace:
at Npgsql.NpgsqlFactory.CreateConnection () [0x00000] in /private/tmp/source/bockbuild/profiles/mono-mac-release/build-root/mono-2.11/_build/mono-2.11.git/mcs/class/Npgsql/Npgsql/NpgsqlFactory.cs:64
at System.Data.Entity.Internal.LazyInternalConnection.CreateConnectionFromProviderName (string) [0x00007] in /private/tmp/source/bockbuild/profiles/mono-mac-release/build-root/mono-2.11/_build/mono-2.11.git/external/entityframework/src/EntityFramework/Internal/LazyInternalConnection.cs:379
at System.Data.Entity.Internal.LazyInternalConnection.InitializeFromConnectionStringSetting (System.Configuration.ConnectionStringSettings) [0x00045] in /private/tmp/source/bockbuild/profiles/mono-mac-release/build-root/mono-2.11/_build/mono-2.11.git/external/entityframework/src/EntityFramework/Internal/LazyInternalConnection.cs:368
at System.Data.Entity.Internal.LazyInternalConnection.TryInitializeFromAppConfig (string,System.Data.Entity.Internal.AppConfig) [0x0000e] in /private/tmp/source/bockbuild/profiles/mono-mac-release/build-root/mono-2.11/_build/mono-2.11.git/external/entityframework/src/EntityFramework/Internal/LazyInternalConnection.cs:310
at System.Data.Entity.Internal.LazyInternalConnection.Initialize () [0x00047] in /private/tmp/source/bockbuild/profiles/mono-mac-release/build-root/mono-2.11/_build/mono-2.11.git/external/entityframework/src/EntityFramework/Internal/LazyInternalConnection.cs:242
at System.Data.Entity.Internal.LazyInternalConnection.get_ProviderName () [0x00000] in /private/tmp/source/bockbuild/profiles/mono-mac-release/build-root/mono-2.11/_build/mono-2.11.git/external/entityframework/src/EntityFramework/Internal/LazyInternalConnection.cs:118
at System.Data.Entity.Internal.LazyInternalContext.get_ProviderName () [0x00000] in /private/tmp/source/bockbuild/profiles/mono-mac-release/build-root/mono-2.11/_build/mono-2.11.git/external/entityframework/src/EntityFramework/Internal/LazyInternalContext.cs:290
at System.Data.Entity.Internal.DefaultModelCacheKeyFactory.Create (System.Data.Entity.DbContext) [0x00022] in /private/tmp/source/bockbuild/profiles/mono-mac-release/build-root/mono-2.11/_build/mono-2.11.git/external/entityframework/src/EntityFramework/Internal/DefaultModelCacheKeyFactory.cs:20
at System.Data.Entity.Internal.LazyInternalContext.InitializeContext () [0x00091] in /private/tmp/source/bockbuild/profiles/mono-mac-release/build-root/mono-2.11/_build/mono-2.11.git/external/entityframework/src/EntityFramework/Internal/LazyInternalContext.cs:388
at System.Data.Entity.Internal.InternalContext.Initialize () [0x00000] in /private/tmp/source/bockbuild/profiles/mono-mac-release/build-root/mono-2.11/_build/mono-2.11.git/external/entityframework/src/EntityFramework/Internal/InternalContext.cs:421
at System.Data.Entity.Internal.InternalContext.GetEntitySetAndBaseTypeForType (System.Type) [0x00000] in /private/tmp/source/bockbuild/profiles/mono-mac-release/build-root/mono-2.11/_build/mono-2.11.git/external/entityframework/src/EntityFramework/Internal/InternalContext.cs:650
at System.Data.Entity.Internal.Linq.InternalSet`1<Web.Users>.Initialize () <0x0006f>
at System.Data.Entity.Internal.Linq.InternalSet`1<Web.Users>.get_InternalContext () <0x00028>
at System.Data.Entity.Internal.Linq.InternalSet`1<Web.Users>.Find (object[]) <0x0002e>
at System.Data.Entity.DbSet`1<Web.Users>.Find (object[]) <0x0002f>
at Web.Controllers.HomeController.Index () [0x0001c] in /Users/nix/Documents/Projects/Dot.NET/Store/Web/Controllers/HomeController.cs:15
at (wrapper dynamic-method) object.lambda_method (System.Runtime.CompilerServices.Closure,System.Web.Mvc.ControllerBase,object[]) <IL 0x00006, 0x0003f>
at System.Web.Mvc.ActionMethodDispatcher.Execute (System.Web.Mvc.ControllerBase,object[]) [0x00000] in /private/tmp/source/bockbuild/profiles/mono-mac-release/build-root/mono-2.11/_build/mono-2.11.git/mcs/class/System.Web.Mvc3/Mvc/ActionMethodDispatcher.cs:27
at System.Web.Mvc.ReflectedActionDescriptor.Execute (System.Web.Mvc.ControllerContext,System.Collections.Generic.IDictionary`2<string, object>) [0x00074] in /private/tmp/source/bockbuild/profiles/mono-mac-release/build-root/mono-2.11/_build/mono-2.11.git/mcs/class/System.Web.Mvc3/Mvc/ReflectedActionDescriptor.cs:84
at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod (System.Web.Mvc.ControllerContext,System.Web.Mvc.ActionDescriptor,System.Collections.Generic.IDictionary`2<string, object>) [0x00000] in /private/tmp/source/bockbuild/profiles/mono-mac-release/build-root/mono-2.11/_build/mono-2.11.git/mcs/class/System.Web.Mvc3/Mvc/ControllerActionInvoker.cs:173
at System.Web.Mvc.ControllerActionInvoker/<InvokeActionMethodWithFilters>c__AnonStorey3B.<>m__46 () [0x00014] in /private/tmp/source/bockbuild/profiles/mono-mac-release/build-root/mono-2.11/_build/mono-2.11.git/mcs/class/System.Web.Mvc3/Mvc/ControllerActionInvoker.cs:216
at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter (System.Web.Mvc.IActionFilter,System.Web.Mvc.ActionExecutingContext,System.Func`1<System.Web.Mvc.ActionExecutedContext>) [0x00033] in /private/tmp/source/bockbuild/profiles/mono-mac-release/build-root/mono-2.11/_build/mono-2.11.git/mcs/class/System.Web.Mvc3/Mvc/ControllerActionInvoker.cs:189

any suggestions or clue about whats going on?

Upvotes: 1

Views: 2154

Answers (2)

Foo Die
Foo Die

Reputation: 36

Two steps to fix:

1) Make sure the default npgsql library that comes with mono is referenced in your references and not one pointing at a specific location that doesn't exist.

2) Throw the Npgsql.dll file for the version of Npgsql that you want to use in the bin directory for your project. It will automatically use this one when you go to run your project or tests.

Upvotes: 2

startupsmith
startupsmith

Reputation: 5764

In my experience this issue is caused by the compiler being confused between the dll and gac versions of Npgsql.

Are you referencing a dll of Npgsql? If you are and you don't require it, try removing the reference and dll and replacing it with the Npgsql package in mono.

If you do require the dll of Npgsql then you will need to remove all references to it from your project replace it in the gac. You can quickly do this by going to the directory of the Npgsql dll and replacing it with your Npgsql dll. The location of the directory will be dependent on your OS.

  • For Ubuntu it is located at: /usr/lib/mono/gac/Npgsql
  • For Mac it is located at: /Library/Frameworks/Mono.framework/Home/lib/mono/gac/Npgsql

Note that by doing this your Npgsql dll may be replaced next time you upgrade Mono.

Upvotes: 1

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