C#連接sqlserver代碼

string connstr = "Persist Security Info=True;User ID=sa;Password=tonhee;Initial Catalog=mynotebook;Data Source=localhost;";
   string sqlstr  = "insert notebook(subject,href,content,type) values('"+Txtsubject.Text+"','"+Txthref.Text+"','"+Txtcontent.Text+"',"+i+")";
   sqlconn = new SqlConnection(connstr);
   sqlconn.Open();
   sqlcmd = new SqlCommand();
   sqlcmd.Connection = sqlconn;
   sqlcmd.CommandText = sqlstr;
   sqlcmd.ExecuteNonQuery();
   sqlcmd.Dispose();
   sqlconn.Close();