c# - insert sql commands by textbox -

i created win forms, , wanna insert sql commands , data database. if put query directly code sql commands, ok, if put query textbox have lot of bugs like:

$exception {"could not find stored procedure 'select * uczniowie'."}
system.exception {system.data.sqlclient.sqlexception } {mateuszlab4.connectdb} mateuszlab4.connectdb question "\"select * uczniowie\"" string datatable {} system.data.datatable sqldatareader null system.data.sqlclient.sqldatareader sqlcommand {system.data.sqlclient.sqlcommand} system.data.sqlclient.sqlcommand

here code:

  private void buttonsearch_click(object sender, eventargs e)           {         string query = textboxquery.text;         connectdb databasewin = new connectdb("(localdb)\\v11.0", "mat");         datagridviewadvanced.datasource = databasewin.datadownload(query);                         } 

when put string query sql commands (for example string query = "select * students" ) working well. if replaced data textbox sth wrong. give me tips guys?

here class datadownloada:

 public datatable datadownload(string question)  {         datatable datatable = new datatable();         sqldatareader sqldatareader;          sqlcommand sqlcommand;           sqlcommand = new sqlcommand(question);         sqlcommand.connection = this.dbconnection;          sqldatareader = sqlcommand.executereader();          datatable.load(sqldatareader);           return datatable;    } 

try code.  public datatable datadownload(string question)  {        using (var ada = new sqldataadapter(question, dbconnection))         {                            // use dataadapter fill datatable             datatable dt = new datatable();             ada.fill(dt);             return dt;           }   }