c# - Populating dropdown list after selecting a value from another dropdown list -

i want able populate dropdown list(ddlexercise) after selecting value dropdown list(ddltype) @ moment getting values ddltype dropdown sql query populating dropdown list when select something, 2nd dropdown list remains empty. have 3 values in ddltype dropdown(gym,core,cardio) , once select 1 of these, using dropdownlist.selectedvalue retrieve corresponding results. here code:

    protected void page_load(object sender, eventargs e)     {        sqlconnection con = new sqlconnection(@"con string");           if (!ispostback)          { bindexercisetype(); }     }       public void bindexercisetype()     {         con.open();         sqlcommand cmd = new sqlcommand("select exercisetype exercisetype", con);         sqldatareader dr = cmd.executereader();         ddltype.datasource = dr;         ddltype.items.clear();         ddltype.items.add("--please select country--");         ddltype.datatextfield = "exercisetype";         ddltype.datavaluefield = "exercisetype";         ddltype.databind();         con.close();        }      public void bindexercise()     {         con.open();         sqlcommand cmd = new sqlcommand("select exercisename exercisedisplay   typename='" + ddltype.selectedvalue + "'", con);         sqldatareader dr = cmd.executereader();         ddlexercise.datasource = dr;         ddlexercise.items.clear();         ddlexercise.items.add("--please select country--");         ddlexercise.datatextfield = "exercisename";         ddlexercise.datavaluefield = "exercisename";         ddlexercise.databind();         con.close();      }          protected void ddlexercise_selectedindexchanged(object sender, eventargs e)     {         bindexercise();     } 

any ideas why may wrong? have autopostback propert set true on both drop down lists. appreciated!

the problem event, event other drop down, event should be:

protected void ddltype_selectedindexchanged(object sender, eventargs e) {     bindexercise(); } 

a contribution code, if populate dropdown datasource, items add not appear if before bind (). must add following, stay latest:

ddltype.items.insert(0, "--please select country--"); 

i hope have been helpful, , luck question. (sorry form english)