Internally I am using a Dictionary<string, list> and when they click the DropDown it retrieves the List() of the corresponding key but I don't see the marked elements.
It only works for me when I have a List instead of a Dictionary for all dropdowns.
Not sure I understand what exactly you are doing however multiple selection of a DropDown using @bind-Value support IList<> and IEnumerable<>. Check the source code for reference.
I have declared this class:
public class FiltersSelected
{
public string key { get;set; } = string.Empty;
public IList List_Selected { get; set; } = new List();
}
I make a loop to draw all the dropdowns
@foreach (Columns column in Columns)
{
var Lista = ElementsFilters.Where(x => x.key ==
key).Select(x=>x.List_Selected).SingleOrDefault().ToList();
Once placed, the selected element does not appear and it does not appear as checked
public async void onChangeFiltros(string key_)
{
var e = ElementsFilters.Where(x => x.key ==
key).Select(x=>x.List_Selected).SingleOrDefault().ToList()
}