c# - Data type mismatch -

i got error when tried select userid database datatable. first userid autonumber, second userid number, , database ms access db.

private void () {     odbcdataadapter ad = new odbcdataadapter("select userid userinfo badgenumber='" + userid + "'", this.fm.cn);     datatable t = new datatable();     ad.fill(t);     ad.dispose();     if (t.rows.count > 0)     {         odbccommand cmd = new odbccommand();         cmd.connection = this.fm.cn;          string id = t.rows[0][0].tostring();         //check date         odbcdataadapter add = new odbcdataadapter("select userid checkinout userid='" + id + "'", this.fm.cn);         datatable tc = new datatable();         add.fill(tc); // <- gotta error here.         add.dispose();     } } 

change query to:

"select userid checkinout userid=" + id 

in sql queries, strings literals (or chars) required enclosed within pair of single quotes ', used delimiter string. delimiter pretty character used identify boundaries - in case of string, single quotes specify string starts , ends.

because of nature of numbers (integers example), not necessary indicate delimiter such single quotes. code failing because when database engine saw single quotes, expecting string, column number datatype, , why obtained data type mismatch error when executing query.