我刚刚开始使用C#进行编程,并且正在阅读将应用程序/网站划分为三个不同层次的文章,这是最佳实践,但我很难理解具体方法.我正致力于一个宠物项目,更多地关注C#,但我不想从任何坏习惯开始.你能看看我有什么,看看我做得对吗？提供一些关于如何将所有内容分解为不同层次的提示建议？
表达层
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>Project: Ruth</title>
<link href="CSS/StyleSheet.css" rel="stylesheet" type="text/css" />
</head>
<body>
<form id="form1" runat="server">
<div class="Body">
<div class="Header">
<div class="Nav">
<img src="images/Header_Main.gif" alt="" width="217" height="101" />
<div class="Menu">
<a href="Default.aspx">
<img src="images/Header_Home-Off.gif" alt="" /></a>
<a href="Default.aspx">
<img src="images/Header_About-Off.gif" alt="" /></a>
<a href="Register.aspx">
<img src="images/Header_Register-Off.gif" alt="" /></a>
<a href="Default.aspx">
<img src="images/Header_Credits-Off.gif" alt="" /></a>
</div>
</div>
</div>
<div class="Content">
<div class="CurrentlyListening">
<asp:Label ID="lblCurrentListen" …我有问题弄清楚为什么我接收"未设置为对象实例的对象引用"此表示层中的错误:
TempAccountManager.Accounts.Add(tempAccount);
我已经使用Visual Studios调试器和帐户获取创建了代码.我相信我有一个访问模块的问题,不确定.
表达层
using myBudget.BusinessObject;
using myBudget.BusinessLogic;
namespace myBudget
{
public partial class NewBudgetWizard : Form
{
public int CurrentStep { get; set; }
public Account TempAccount = new Account();
public AccountManager TempAccountManager = new AccountManager();
public NewBudgetWizard()
{
private void createAccountList(ListView lvAccounts)
{
foreach (ListViewItem lvi in lvAccounts.Items)
{
int tempAccNumber = Int32.Parse(lvi.SubItems[0].Text);
string tempAccName = lvi.SubItems[1].Text;
string tempAccType = lvi.SubItems[2].Text;
decimal tempAccBalance = decimal.Parse(lvi.SubItems[3].Text, System.Globalization.NumberStyles.Currency);
Account tempAccount = new Account(tempAccNumber, tempAccName, tempAccType, tempAccBalance, DateTime.Now);
TempAccount = …c# oop access-modifiers object-reference nullreferenceexception