如何使用LIKE和%%运算符在web表单中查询和筛选我的数据?

我想使用LIKE和%%operator从我的web表单中的sql server中筛选和选择数据

我在stackoverflow解决方案中进行了搜索,但我找不到我的案例的解决方案,我尝试了很多,但都没有正常工作。这是我的代码:

protected void BtnSearch_Click(object sender, EventArgs e)
            {
                string sql = @" SELECT [appt_id],visitor_name,mobile ,work_place.work_place_name as work_place_name,days.day as day,date,[time],[subject],[duration],appointment_place.appt_place as appt_place 
                               FROM [Appointments] 
                               inner join days on days.day_id = Appointments.day_id 
                               inner join appointment_place on appointment_place.appt_place_id =Appointments.appt_place_id
                               inner join work_place on work_place.work_place_id = Appointments.work_place_id 
                               where 1=1 ";

                string condition = "";
                string orderby = "order by date";
                // orderby += "order by appointments.time";

                if (txtVisitorName.Text != "")
                {
                    condition += " and appointments.visitor_name like '" + txtVisitorName.Text + "'";
                }
                if (txtsubject.Text != "")
                {
                    condition += " and appointments.subject like '" + txtsubject.Text + "'";
                }
                if (txtMobileNo.Text != "")
                {
                    condition += " and appointments.mobile ='" + txtMobileNo.Text + "'";
                }


                DataTable dt = func.fireDatatable(string.Format(sql + condition + orderby));
                gvappt.DataSource = dt;
                gvappt.DataBind();
            }

我希望代码的输出使用LIKE和%%来搜索访客姓名或主题是否包含部分姓名或部分主题?