Может быть, что-то вроде этого:
var dt=new DataTable();
dt.Columns.Add("id_staff",typeof(int));
dt.Columns.Add("name_staff",typeof(string));
var dt2=new DataTable();
dt2.Columns.Add("id_staff",typeof(int));
dt2.Columns.Add("name_staff",typeof(string));
dt.Rows.Add(1,"test");
dt2.Rows.Add(2,"test2");
var result=
(
from datatable1 in dt.AsEnumerable()
select new
{
id_staff=datatable1.Field<int>("id_staff"),
name_staff=datatable1.Field<string>("name_staff")
}
).Concat
(
from datatable2 in dt2.AsEnumerable()
select new
{
id_staff=datatable2.Field<int>("id_staff"),
name_staff=datatable2.Field<string>("name_staff")
}
);