SelectedValues not working in MultiSelectList mvc

Question

I have a class like

 public class Category
    {
        public int ID { get; set; }
        public string Name { get; set; }
        public ICollection

        

Answer 1

The last parameter of the MultiSelectList constructor takes an array of selected Id's not a collection of Category complex types.

If you change it to this instead it will work as expected:

product.Categories = new MultiSelectList(list, "ID", "Name", cat.CategorySelected.Select(c => c.ID).ToArray());

It simply projects it into an array of Id's instead.

See below screen shot:

Ps I also had to add this to the constructor of Category to initialize the collection:

public Category()
{
   CategorySelected = new List<Category>();
}