textbox value change in c# -

if textbox value has changed, how can select database new textbox value , not old value?

string constring = "datasource=127.0.0.1;username=root;password=admin"; string query = "select * mohamed.usercompany1 office  =  '" + textbox1.text + "'  ;"; mysqlconnection condatabase = new mysqlconnection(constring); mysqlcommand cmddatabase = new mysqlcommand(query, condatabase); dataset dataset1 = new dataset(); mysqldatareader myreader; try {     condatabase.open();     myreader = cmddatabase.executereader();     if (myreader.read())     {         string scode = myreader.getint32("techname").tostring();         textbox1.text = (string)myreader["techname"];         combobox2.items.add(scode).tostring();         listview1.items.add(scode).tostring();         this.refresh();     } } catch (exception ex) {     messagebox.show(ex.message); } 

you can add handler textchanged event. raised when text changed.

private void textbox1_textchanged(object sender, eventargs e) {     //textbox1.text contains new text     //execute sql... } 

but should careful. possible input sql statement in textbox, damages database. more secure use parameters:
parameterized query mysql c#