webservice + database

I want insert some data to database. I wrote this simple method in webservice but it is don't work why?

public string zapisz(string data_newsa,string autor,string email, string tresc, string temat)
{
string stan;
DataRow nowy = dataSet11.news_select.NewRow();
nowy["data_newsa"]=data_newsa;
nowy["autor"]=autor;
nowy["email"]=email;
nowy["tresc"]=tresc;
nowy["temat"]=temat;
dataSet11.news_select.Rows.Add(nowy);
sqlDataAdapter1.Update(dataSet11,"newsy_select");
stan=sqlDataAdapter1.InsertCommand.Parameters[8].Value.ToString();
return stan;

what i make wrong and haw it should be done