c# - Must declare a scalar variable -

i getting exception "must declare scalar variable"@straccountid"

string @straccountid = string.empty;  ssql = "select gub.btn,        gup.cust_username,        gup.email   gbs_user_btn         gub,        gbs_user_profile     gup  gub.cust_uid = gup.cust_uid        , gub.btn = '@straccountid' order        create_date desc"  @straccountid = straccountid.substring(0, 10); 

code running query against db

    try                 {                     ocn = new sqlconnection(configurationsettings.appsettings["gbregistrationconnstr"].tostring());                     ocn.open();                     ocmd = new sqlcommand();       ocmd.parameters.addwithvalue("@straccountid", straccountid);                        ocmd.commandtext = ssql;                     ocmd.connection = ocn;                     ocmd.commandtype = commandtype.text;                      odr = ocmd.executereader(commandbehavior.closeconnection); 

i declared variable. there flaw in query?

first off bat rid of these 2 lines:

string @straccountid = string.empty; @straccountid = straccountid.substring(0, 10); 

and try code:

string straccountid = "a1234"; //create variable , assign value string acctid = straccountid.substring(0, 10);  ocn = new sqlconnection(configurationsettings.appsettings["gbregistrationconnstr"].tostring()); ocn.open(); ocmd = new sqlcommand();          ocmd.commandtext = ssql; ocmd.connection = ocn; ocmd.commandtype = commandtype.text; ocmd.parameters.add("straccountid", acctid); //<-- forgot add in parameter odr = ocmd.executereader(commandbehavior.closeconnection); 

here link on how create parametized query: http://www.dotnetperls.com/sqlparameter