DropDownListFor a collection not selecting value

Question

I'm using a strongly typed view with a custom viewmodel. This viewmodel contains a collection of books.

public IList<Books> Books { get; private set; }

I'm also passing a select-list to the view. However the DropDownListFor helper class doesn't automatically preselect the default value of the book.

@Html.DropDownListFor(m => Model.Books[i].AuthorID, Model.Author as SelectList)

Everything else works, e.g. it does pass the selected value back to the controller.

I figured out a workaround by creating the select list in the viewmodel:

@Html.DropDownListFor(m => Model.Books[i].AuthorID, new SelectList(Model.AuthorList, "Value", "Text", @Model.Books[i].AuthorID.ToString()))

However I don't want to implement this workaround if there is a simpler solution. is there a way that the view can handle values from a collection?

Answer 1

You should be passing the list of authors as part of your model as you have in your workaround. You can generate the select list in the controller however, it isn't a requirement to create the list in the view. Something like:

@Html.DropDownListFor(m => Model.Books[i].AuthorID, Model.AuthorList)

This would work if you create the list in the controller:

var model = new ViewModel()
{
    AuthorList = new SelectList(Model.AuthorList, "Value", "Text"),
};

And it will handle setting the selected item on it's own.

As for why your Model.Author as SelectList isn't working, I'm guessing Model.Author is not a list of author names and IDs. It's probably a domain object and casting it using as is returning null.