Unity 3 and Error "The type name or alias "xxxxx" could not be resolved. Please check your configuration file and verify this type name."

Question

Is there any way to resolve this problem with Unity 3 ?

I have made all that is possible to bypass this message error, but I can't resolve; I have already did everything I've seen in googles searches.

I am almost giving up and trying another DI solution.

My configuration file:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <configSections>
    <section name="unity" type="Microsoft.Practices.Unity.Configuration.UnityConfigurationSection, Microsoft.Practices.Unity.Configuration" />
  </configSections>
  <unity xmlns="http://schemas.microsoft.com/practices/2010/unity">
    <assembly name="Biblioteca" />
    <assembly name="Biblioteca.Contracts" />
    <assembly name="Biblioteca.Business" />
    <namespace name="Biblioteca" />
    <namespace name="Biblioteca.Contracts" />
    <namespace name="Biblioteca.Business" />
      <container>
        <register type="Biblioteca.Contracts.IManterCategoriaBO" mapTo="Biblioteca.Business.ManterCategoriaBO" />
      </container>
  </unity>
</configuration>

My interface:

using Biblioteca.Transport;
using System.Linq;

namespace Biblioteca.Contracts
{
    public interface IManterCategoriaBO
    {
        IQueryable<CategoriaDTO> GetAll();
        CategoriaDTO GetById(int id);
        void Insert(CategoriaDTO dto);
    }
}

My concrete class:

using Biblioteca.Contracts;
using Biblioteca.Transport;
using Biblioteca.Data;
using System;
using System.Linq;

namespace Biblioteca.Business
{
    public class ManterCategoriaBO : IManterCategoriaBO
    {
        public CategoriaDTO GetById(int id)
        {
            CategoriaDTO dto = new CategoriaDTO();
            ManterCategoriaDO categoriaDO = new ManterCategoriaDO();

            dto = categoriaDO.GetById(1);

            return dto;
        }

        public IQueryable<CategoriaDTO> GetAll()
        {
            throw new NotImplementedException();
        }

        public void Insert(CategoriaDTO dto)
        {
            throw new NotImplementedException();
        }
    }
}

My Global.asax:

using System.Web.Http;
using System.Web.Mvc;
using System.Web.Optimization;
using System.Web.Routing;
using Biblioteca.Dependency;

namespace Biblioteca
{
    // Note: For instructions on enabling IIS6 or IIS7 classic mode, 
    // visit http://go.microsoft.com/?LinkId=9394801

    public class MvcApplication : System.Web.HttpApplication
    {
        protected void Application_Start()
        {
            AreaRegistration.RegisterAllAreas();

            WebApiConfig.Register(GlobalConfiguration.Configuration);
            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
            RouteConfig.RegisterRoutes(RouteTable.Routes);
            BundleConfig.RegisterBundles(BundleTable.Bundles);

            //Below is a static variable to take the unity container
            //which is on a dependency project
            Global.Container = Bootstrapper.Initialise();
        }
    }
}

My Bootstrapper class:

using Microsoft.Practices.Unity;
using Microsoft.Practices.Unity.Configuration;
using System.Configuration;
using System.Web.Mvc;
using Unity.Mvc4;

namespace Biblioteca
{
    public static class Bootstrapper
    {
        public static IUnityContainer Initialise()
        {
            var container = BuildUnityContainer();

            DependencyResolver.SetResolver(new UnityDependencyResolver(container));

            return container;
        }

        private static IUnityContainer BuildUnityContainer()
        {
            string path = ConfigurationManager.AppSettings["UnityConfigFilePath"].ToString();

            var fileMap = new ExeConfigurationFileMap() { ExeConfigFilename = path + "\\Unity.config" };

            System.Configuration.Configuration configuration = ConfigurationManager.OpenMappedExeConfiguration(fileMap, ConfigurationUserLevel.None);

            var unitySection = (UnityConfigurationSection)configuration.GetSection("unity");

            //*** this line is firing the error !!! ****
            var container = new UnityContainer().LoadConfiguration(unitySection);

            return container;
        }
    }
}

My Dependency project static class:

using Microsoft.Practices.Unity;

namespace Biblioteca.Dependency
{
    public static class Global
    {
        public static IUnityContainer Container = null;

        public static T Resolve<T>()
        {
            return Container.Resolve<T>();
        }
    }
}

My UI model class file on MVC 4 project. I am using 4.5 framework.

using Biblioteca.Contracts;
using Biblioteca.Dependency;

namespace Biblioteca.Models
{
    public class LivroModel
    {
        public void GetAll()
        {
            if (Global.Container != null)
            {
                var categoriaBO = Global.Resolve<IManterCategoriaBO>();
                categoriaBO.GetById(1);
            }
        }
    }
}

I think everything is in the right way. But, I can´t see this DI works cause I got an error just in the mapping process, in line below on my Bootstrapper class, BuildUnityContainer method:

var container = new UnityContainer().LoadConfiguration(unitySection);

The error is:

The type name or alias Biblioteca.Contracts.IManterCategoriaBO could not be resolved. Please check your configuration file and verify this type name.

I have double checked all my classes and for me, they are ok. Or is it missing anything ?

Answer 1

The problem is in you config file. You are mixing two concepts with some incorrect syntax.

The <assembly... /> and <namespace ... /> nodes provide an assembly and namespace search order when your <register ... /> node contains a type that cannot be found by itself. If a type cannot be found, it searches through all combinations of [namespace].Type, [assembly]. Here's where the error is: it does NOT search for Type, [assembly]. If any <namespace ... /> nodes are defined, it does NOT try appending only the assembly.

So your <register type="Biblioteca.Contracts.IManterCategoriaBO" mapTo="Biblioteca.Business.ManterCategoriaBO" /> node has the type Biblioteca.Contracts.IManterCategoriaBO which does not contain the assembly, so it cannot be found. Therefore, it needs to do a search. You did specify <namespace ... /> nodes, so it will first try Biblioteca.Biblioteca.Contracts.IManterCategoriaBO, Biblioteca. Notice the duplicate Biblioteca name.

Here's a corrected config file.

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <configSections>
    <section name="unity" type="Microsoft.Practices.Unity.Configuration.UnityConfigurationSection, Microsoft.Practices.Unity.Configuration" />
  </configSections>
  <unity xmlns="http://schemas.microsoft.com/practices/2010/unity">
    <assembly name="Biblioteca" />
    <assembly name="Biblioteca.Contracts" />
    <assembly name="Biblioteca.Business" />
    <namespace name="Biblioteca" />
    <namespace name="Biblioteca.Contracts" />
    <namespace name="Biblioteca.Business" />
    <container>
      <register type="IManterCategoriaBO" mapTo="ManterCategoriaBO" />
      <!-- Or this works -->
      <!--<register type="Biblioteca.Contracts.IManterCategoriaBO, Biblioteca" mapTo="Biblioteca.Business.ManterCategoriaBO, Biblioteca" />-->
    </container>
  </unity>
</configuration>