Question

Delete multiple rows by using the following conditions ، But the error..

        Melks = Ent.Tbl_Melk.Where(d => d.Mantaghe == Mantaghe && d.Hoze == Hoze && d.Block == Block && d.Melk == Melk).All();
        Ent.DeleteObject(Melks);
        int r = Ent.SaveChanges();
        if (r > 0)
        {
            return true;
        }
        else
        {
            return false;
        }

Answer 1

Looking at your code it seems that Melks is a boolean variable. You cannot call DeleteObject() supplying a boolean as the argument.

You need to remove the .All() predicate at the end of your LINQ statement and then delete each object returned by the query:

var melks = Ent.Tbl_Melk.Where(
  d => d.Mantaghe == Mantaghe && d.Hoze == Hoze && d.Block == Block && d.Melk == Melk);
foreach (var melk in melks)
  Ent.DeleteObject(melk);