Visual C++ using parameters with MySqlDataAdapter -

i trying make simple login screen without encryption part (i have make research on later). college project , still starting learn. , having troubles code or whatever think exception catching error , printing me.

here's code:

        string^ user = usertxt->text;         string^ pass = pwtxt->text;          try{              cn->connectionstring = cninfo;             cn->open();              string^ loginquery = "select * acceso user_id = @auser , user_pass = @apass;";              logincmd = gcnew mysqlcommand(loginquery, cn);             cmdadp->selectcommand = logincmd;             logincmd->commandtype = commandtype::text;             logincmd->parameters->addwithvalue("@auser", user);             logincmd->parameters->addwithvalue("@apass", pass);              cmdadp->fill(table);              if (table->rows->count > 0) {                  messagebox::show("login success");                 //in here launch other form                 application::run(gcnew turismo::myform);                 exitbtn_click(sender, e);                 table->rows->clear();              }             else{                  messagebox::show("login error: incorrect login info");                 table->rows->clear();              }          }         catch (exception^ ex){             messagebox::show(ex->message);         }         finally{             cn->close();         } 

sorry lack of documentation. in bit of hurry finish it.

logincmd = gcnew mysqlcommand(loginquery, cn); cmdadp->selectcommand = logincmd; logincmd->commandtype = commandtype::text; logincmd->parameters->addwithvalue("@auser", user); logincmd->parameters->addwithvalue("@apass", pass); 

this part got researching on "how use parameters command adapter". , @ end of program when click on login, on exception message:

reference object not stablished intance of object.