c# - How to set dropdown list value and item as database table value in edit? -

when click edit button form filling database values in textbox dropdown list..

textbox values set. can't set dropdownlist values..

the code is;

sqlconnection con = new sqlconnection(system.web.configuration.webconfigurationmanager.connectionstrings["connectionstring"].connectionstring); con.open(); string str = "select * master id='" + id + "'"; sqlcommand command = new sqlcommand(str, con); sqldatareader reader = command.executereader(); while (reader.read()) {       ddcustomername.datavaluefield = reader["customerid"].tostring();       txtpickuplocation.text = reader["location"].tostring(); } con.close();    

use selectedvalue property  while (reader.read()) {     ddcustomername.selectedvalue= reader["customerid"].tostring();     txtpickuplocation.text = reader["location"].tostring(); }