ASP.NET MVC: No parameterless constructor defined for this object

This can also be caused if your Model is using a SelectList, as this has no parameterless constructor:

public class MyViewModel
{
    public SelectList Contacts { get;set; }
}

You'll need to refactor your model to do it a different way if this is the cause. So using an IEnumerable<Contact> and writing an extension method that creates the drop down list with the different property definitions:

public class MyViewModel
{
    public Contact SelectedContact { get;set; }
    public IEnumerable<Contact> Contacts { get;set; }
}

public static MvcHtmlString DropDownListForContacts(this HtmlHelper helper, IEnumerable<Contact> contacts, string name, Contact selectedContact)
{
    // Create a List<SelectListItem>, populate it, return DropDownList(..)
}

Or you can use the @Mark and @krilovich approach, just need replace SelectList to IEnumerable, it's works with MultiSelectList too.

 public class MyViewModel
    {
        public Contact SelectedContact { get;set; }
        public IEnumerable<SelectListItem> Contacts { get;set; }
    }

I just had a similar problem. The same exception occurs when a Model has no parameterless constructor.

The call stack was figuring a method responsible for creating a new instance of a model.

System.Web.Mvc.DefaultModelBinder.CreateModel(ControllerContext controllerContext, ModelBindingContext bindingContext, Type modelType)

---

Here is a sample:

public class MyController : Controller
{
    public ActionResult Action(MyModel model)
    {

    }
}

public class MyModel
{
    public MyModel(IHelper helper) // MVC cannot call that
    {
        // ...
    }

    public MyModel() // MVC can call that
    {
    }
}

You need the action that corresponds to the controller to not have a parameter.

Looks like for the controller / action combination you have:

public ActionResult Action(int parameter)
{

}

but you need

public ActionResult Action()
{

}

Also, check out Phil Haack's Route Debugger to troubleshoot routes.