List Alist = new List();
List Blist = new List();
int CountBList = Blist.Count;
for (int i = 0; i < Alist.Count; i++)
{
if (CountBList != i)
{
for (int x = 0; x < Blist.Count; x++)
{
if (Alist[i].ToString() != Blist[x].ToString())
{
Alist.Add(Blist[x].ToString());
}
}
}

}