The model item passed into the dictionary is of type 'System.Collections.Generic.List' but this dictionary requires a model item of type 'System.Collections.Generic.IEnumberable'

Posted on 2014-03-18
Last Modified: 2014-03-23
I have an MVC 4 application that has a model developed using EF 5.0 (Code First).  I am investigating TDD and had to make changes to the code generated by the model in order to get my unit tests to work.  Now that my unit tests work I am getting the following error when I try and run the application.

System.InvalidOperationException: The model item passed into the dictionary is of type 'System.Collections.Generic.List`1[AppCatalog.Models.AppCatalog_Database]', but this dictionary requires a model item of type 'System.Collections.Generic.IEnumerable`1[AppCatalogData.AppCatalog_Database]'.

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Here is my controller:
namespace AppCatalog.Controllers
    public class DBCatalogController : Controller
        private IAppCatalog db { get; set; }

        public DBCatalogController(IAppCatalog dataContext = null)
            db = dataContext ?? new AppCatalogContainer();
        public DBCatalogController()
            db = new AppCatalogContainer();

        // GET: /DBCatalog/

        public ViewResult Index()
            ViewBag.Title = "Application Catalog -> Database Catalog";

            var appcatalog_database = db.AppCatalog_Database.Include(a => a.AppCatalog_ServerType);
            return View(appcatalog_database.ToList());

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Here is the model definition in my view:
@model IEnumerable<AppCatalogData.AppCatalog_Database>

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Here is my Interface definition:
namespace AppCatalog.Models 
    public interface IAppCatalog 
        IDbSet<AppCatalog_Database> AppCatalog_Database { get; set; }
        IDbSet<AppCatalog_ServerType> AppCatalog_ServerType { get; set; }
        IDbSet<AppCatalog_DBConnection> AppCatalog_DBConnection { get; set; }
        IDbSet<AppCatalog_Environment> AppCatalog_Environment { get; set; }
        IDbSet<AppCatalog_PIIData> AppCatalog_PIIData { get; set; }
        IDbSet<AppCatalog_Application> AppCatalog_Application { get; set; }
        IDbSet<AppCatalog_ApplicationTable> AppCatalog_ApplicationTable { get; set; }

        int SaveChanges();
        void Dispose();

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Here is the AppCatalogContainer definition:
namespace AppCatalog.Models
    using System;
    using System.Data.Entity;
    using System.Data.Entity.Infrastructure;
    public partial class AppCatalogContainer : DbContext, IAppCatalog
        public AppCatalogContainer()
            : base("name=AppCatalogContainer")
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
            throw new UnintentionalCodeFirstException();
        public IDbSet<AppCatalog_Database> AppCatalog_Database { get; set; }
        public IDbSet<AppCatalog_ServerType> AppCatalog_ServerType { get; set; }
        public IDbSet<AppCatalog_DBConnection> AppCatalog_DBConnection { get; set; }
        public IDbSet<AppCatalog_Environment> AppCatalog_Environment { get; set; }
        public IDbSet<AppCatalog_PIIData> AppCatalog_PIIData { get; set; }
        public IDbSet<AppCatalog_Application> AppCatalog_Application { get; set; }
        public IDbSet<AppCatalog_ApplicationTable> AppCatalog_ApplicationTable { get; set; }

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I'm not sure what change I need to make to the View or the Controller to get this to work.  Everything worked fine until I made the changes for the unit testing.

Any help is greatly appreciated!
Question by:dyarosh
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Expert Comment

by:Daniel Van Der Werken
ID: 39937343
Well, it looks like you are returning a List() and it is expecting an IEnumerable<> back.

So, I think these lines of code are the issue:

var appcatalog_database = db.AppCatalog_Database.Include(a => a.AppCatalog_ServerType);
return View(appcatalog_database.ToList());

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Instead of doing the .ToList(), do as documented here:

I would do:

return View(appcatalog_database.IEnumerable<AppCatalogData.AppCatalog_Database>().GetEnumerator();

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...or something like that. I don't have your code, so I can't fiddle with it.

Accepted Solution

dyarosh earned 0 total points
ID: 39937486
I found the problem.  I had to make sure my model derived from DbContext and my interface (IAppCatalog).

Author Closing Comment

ID: 39948428
I found the problem on my own.

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