private void frmchitietmuonsach_Load(object sender, EventArgs e) { ChiTietPhieuMuon chitiet = new ChiTietPhieuMuon(); cbbmasach.DataSource = da.Convert(da.Query("Select ten from Sach")); cbbnhaxuatban.DataSource = da.Convert(da.Query("select ten from Nhaxuatban")); cbbtacgia.DataSource = da.Convert(da.Query("select ten from Tacgia")); cbbtheloai.DataSource = da.Convert(da.Query("select ten from TheLoai")); List <Object> lst = new List <object>(); lst = da.Convert(da.Query("select max(ma) from PhieuMuon")); txtphieumuon.Text = lst[0].ToString(); if (txtphieumuon.Text != null) { chitiet.phieumuonma = txtphieumuon.Text; DSChitietphieumuon.DataSource = da.Query("DanhSachChiTietPhieuMuon", new SqlParameter("@phieumuonma", chitiet.phieumuonma)); } }