Question

I am building a test application using MVC3, Razor, and Entity Framework 4.1 with a schema-first approach (as apposed to a code-first approach), in a repository pattern. I would like to avoid accessing data objects in my view, and access a model instead, but I am having a problem. As far as I can tell, the data objects are being returned from the data layer as ObjectSet, but my View needs IEnumerable, and I don’t know how to cast one to the other.

Here is some code, to help clarify.

---

Model …

namespace TestSolution.Models
{
    public class ProjectModel
    {
        [HiddenInput]
        public int Id { get; set; }

        [Required]
        [StringLength(255, ErrorMessage = "The name cannot be more than 255 characters long.")]
        [Display(Name = "Name")]
        public string Name { get; set; }

        [Required]
        [Display(Name = "Description")]
        public string Description { get; set; }
    }
}

Repository …

public IQueryable<ProjectModel> GetProjects()
{
    return Db.Project;
}

Entities …

public ObjectSet<Project> Project
{
    get
    {
        if ((_Project == null))
        {
            _Project = base.CreateObjectSet<Project>("Project");
        }
        return _Project;
    }
}

Controller …

public ActionResult Index()
{
    IEnumerable<TestSolution.Models.ProjectModel> model = _projectRepository.GetProjects();
    return View(model);
}

View …

@model IEnumerable<TestSolution.Models.ProjectModel>

Error I am getting when building …

Cannot implicitly convert type 'System.Data.Objects.ObjectSet<TestSolution.Project>' to 'System.Linq.IQueryable<TestSolution.Models.ProjectModel>'. An explicit conversion exists (are you missing a cast?)

---

Does this question make sense? I am just not sure where go from here … any advise you guys can give me would be awesome. 🙂

EDIT: I was able to solve this with Kyle’s suggestion by changing my Repository code to …

public IQueryable<ProjectModel> GetProjects()
{
  return Db.Project.Select(i => new ProjectModel() { Id = i.Id, Name = i.Name, Description = i.Description });
}

Answer 1

The problem isn’t converting from ObjectSet<T> to IEnumerable<T> (ObjectSet<T> implements IEnumerable<T>).

The problem is converting from TestSolution.Project to TestSolution.Models.ProjectModel. You will need to write some conversion code, maybe something similar to the below:

model.Select(i => new ProjectModel() { /* Set properties here. */ });