ADO.net 中 数据库操作的基本方法

protected string ConnectSqlServer()    {        string sResult = "";        string connectStr = "Server=localhost;uid=sa;pwd=sa;database=BiaoWH";        mySqlConnection = new SqlConnection(connecyStr);        try        {            mySqlConnection.Open();        }        catch (Exception e)        {            sResult=e.Message;        }        return sResult;    }

    protected DataTable Search(string strSqlcmd)    {        DataSet ds = new DataSet();        DataTable dt = new DataTable();        try        {            SqlDataAdapter mySqlDataAdapter = new SqlDataAdapter(strSqlcmd,connectStr);            mySqlDataAdapter.Fill(ds, "Customers");            dt = ds.Tables[0];            ds.Tables.Remove(dt);        }        catch(Exception e)        {            string exm = e.Message;            return null;        }        return dt;    }