Corrected code...
con = new SqlConnection("Server=(local);initial catalog=master;Trusted_Connection=True");
con.Open();
SqlCommand cmd = new SqlCommand("delete Employee where EmployeeID=@EmployeeID", con);
cmd.CommandType = CommandType.Text;
cmd.Parameters.Add(new SqlParameter("@EmployeeID", DropDownList1.SelectedValue));
cmd.ExecuteNonQuery();
You should be careful while copy-pasting the code..