asp.net - how to map a checkbox to update the database after submit. -

i need use session datatable email value @email , base dropdownlist.

protected void page_load(object sender, eventargs e)     {         dropdownlist1.datasource = (datatable)session["dt"];         dropdownlist1.datavaluefield = "base";         dropdownlist1.datatextfield = "base";         dropdownlist1.databind();      }       string str;      protected void submit_click(object sender, eventargs e)     {         if (checkbox9.checked == true)         {             str = str + checkbox9.text + "x";         }                }      sqlconnection con = new sqlconnection(...);     string sql = "update inquiry2 set question1 = @str email = @email , base = @base;";      con.open();      sqlcommand cmd = new sqlcommand(sql, con);       cmd.parameters.addwithvalue("@email", session.dt.email);     cmd.parameters.addwithvalue("@str", str);     cmd.parameters.addwithvalue("@base", dropdownlist1.base); } 

}

your syntax reading value out of session wrong, cannot use session.dt.email.

you need read datatable out of session , cast datatable, this:

datatable thedatatable = null;  // verify dt in session before trying if(session["dt"] != null) {     thedatatable = session["dt"] datatable; }  string email;  // verify data table not null if(thedatatable != null) {     email = datatable.rows[0]["email"].tostring(); } 

now can use email string value in sql command parameters, this:

cmd.parameters.addwithvalue("@email", email); 

update:

you want wrap drop down list binding in page_load check ispostback, because code posted bind drop down list every time page loads, not first time, destroying whatever selection user made.

instead this:

protected void page_load(object sender, eventargs e) {     if(!ispostback)     {         dropdownlist1.datasource = (datatable)session["dt"];         dropdownlist1.datavaluefield = "base";         dropdownlist1.datatextfield = "base";         dropdownlist1.databind();     } } 

now base value in database parameter logic should value user selected.