BackUp Code in LinQ :            

            string str_filename = "";  
            SaveFileDialog sfd = new SaveFileDialog();
            sfd.FileName = DateTime.Now.ToString("ddmmyyyy"); 
            sfd.Filter = "BackUp Files(*.bak)|*.bak";
            if (sfd.ShowDialog() == DialogResult.OK) 
            {
                str_filename = sfd.FileName;
                try
                {
                    
                    db.ExecuteCommand("USE master; BACKUP DATABASE " + db_name + " TO DISK ='" + str_filename + "'");
                    MessageBox.Show("پشتيباني گيري با موفقيت انجام شد", "", MessageBoxButtons.OK, MessageBoxIcon.Information);
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message, "", MessageBoxButtons.OK, MessageBoxIcon.Information);
                }
            }

Restore Code in LinQ :

            string str_filename = "";
            OpenFileDialog opd = new OpenFileDialog();
            opd.Filter = "BackUp Files (*.bak)|*.bak";
            if (opd.ShowDialog() == DialogResult.OK)
            {
                str_filename = opd.FileName;
                try
                {
                    db.ExecuteCommand("USE master; RESTORE DATABASE " + db_name + " FROM DISK = '" +str_filename+ "'");
                    MessageBox.Show("عمليات بازيابي با موفقيت انجام شد", "", MessageBoxButtons.OK, MessageBoxIcon.Information);
                    Application.Restart();

                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message, "", MessageBoxButtons.OK, MessageBoxIcon.Information);
                }
            }