请为以下每句代码写上注释 SqlConnectionconn = new SqlConnection();//(1) conn.ConnectionString = "server=.;database=library;integrated security=true";//(2) SqlCommand com = new SqlCommand();//(3) com.CommandText = "updatetbl_user set password='123'";//(4) com.Connection = conn;//(5) com.CommandType = CommandType.Text;//(6) try { conn.Open();//(7) int num= com.ExecuteNonQuery(); //(8) MessageBox.Show(num.ToString());//(9) } catch (Exception ex) { MessageBox.Show(ex.Message); //(10) } finally { if(conn.State==ConnectionState.Open )//(11) { conn.Close(); //(12) } }