refresh current asp.net form using c#

Clear the items of dropdownlist
like
DropDownList1.Items.Clear();
and then add new items in dropdownlist.

hello sir;
i want to fetch data from the grid of "opd info" in the dropdownlist such as pv id,patient reg code,doctor id, charges of "patient visit" form. if i press fetch button first time then the data fetched normally. but i fetched 2nd and 3rd time the new data placed normally in the dropdownlist of "patient visit" form . but the old data is duplicating . it means the old data comes twice and so on. i want to overright old data in these dropdownlists. i am sending my fetch button code and also screen shots.

From your code i think so you need to add values in dropdownlist in which you want to add the values dynamically with database change if it is like then try like this

protected void Page_Load(object sender, EventArgs e)

        {

           TextBox_pv_date.Text= System.DateTime.Now.ToLongDateString();

         

               DropDownList_patient_reg_code.Items.Add("Choose");

               SqlCommand cmd = new SqlCommand("select * from [clinic patient registartion]", connection.get());

               SqlDataReader read = cmd.ExecuteReader();

                while (read.Read())

                {

               DropDownList_patient_reg_code.Items.Add(read["patient reg code"].ToString());

                }

                read.Close();

 

                DropDownList_patient_visit_pv_id.Items.Add("choose");

                dropdown_list_patient_visit_OPD_CHARGES.Items.Add("choose");

                DropDownList_patient_visit_patient_reg_code.Items.Add("choose");

                doctor_id_list.Items.Add("choose");

                SqlCommand cmd1 = new SqlCommand("select * from [clinic opd info]", connection.get());

                SqlDataReader read1 = cmd1.ExecuteReader();

                while (read1.Read())

                {

                   DropDownList_patient_visit_pv_id.Items.Add(read1["pv id"].ToString());

                   dropdown_list_patient_visit_OPD_CHARGES.Items.Add(read1["opd charges"].ToString());

                   DropDownList_patient_visit_patient_reg_code.Items.Add(read1["patient reg code"].ToString());

                   doctor_id_list.Items.Add(read1["doctor id"].ToString());

 

                }

                read1.Close();

 

}

and one more thing put the breakpoint on refresh click event check it is working or not if it is not working then on your page validation is there so set property of refresh button CausesValidation to false.

no effect. but this is my code of form load.

any postback can refresh your form. just set autopostback property to true of refresh button. And one more thing bind your controls in page_load event without using if(!IsPostBack).