There is no ViewData item of type ‘IEnumerable’ that has the key country

If you were using DropDownListFor like this:

@Html.DropDownListFor(m => m.SelectedItemId, Model.MySelectList)

where MySelectList in the model was a property of type SelectList, this error could be thrown if the property was null.

Avoid this by simply initializing it in constructor, like this:

public MyModel()
{
    MySelectList = new SelectList(new List<string>()); // empty list of anything...
}

This often happens in POST actions. Make sure you assign something before re-rendering the view.