Select listbox items using comma separated values in MVC?

See more:

ListBox

C#5.0

MVC5

ASP.NET5

C#7.0

I am saving the selected ListBox items values in a comma separated string.

private string fabricString(IEnumerable<string> fabricsList)
    {
        string str = string.Join(",", fabricsList);
        return str;
    }

For Example str = "1,3"

Now in edit controller how can I want to select Text in ListBox based on the above string

What I have tried:

public ActionResult Edit(int? id)
    {

        if (id == null)
        {
            return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
        }
        fa_Data fad_Data = db.fad_Data.Find(id);
        fad_Data.sizeList = fad_Data.size.Split(',').ToList().Select(s => new SelectListItem() { Text = s, Value = s });
        if (fad_Data == null)
        {
            return HttpNotFound();
        }
        return View(fad_Data);
    }

Using above code I get the error

An exception of type 'System.ArgumentNullException' occurred in System.Web.Mvc.dll but was not handled in user code at line

fad_Data.sizeList = fad_Data.size.Split(',').ToList().Select(s => new SelectListItem() { Text = s, Value = s });