最近做个一个EntityFramework的DEMO,刚开始做的时候在删除跟修改数据时采取的是根据ID查询到对应实体，然后再删除和更新实体，发现这样做多查询了一次数据库。尤其是做修改的时候，还得每个属性进行赋值修改，加大了代码量。 因此寻找另一条出路，思路大概是这样的：首先获取需要修改或者删除的对象，根据EntityKey判断上下文中是否存在，假如存在，则移除上下文中的对象。然后把获取到的对象附加到对象上下文中，再将上下文更新保存的数据库。
1 public void Update(Student entity)
2 {
3 entity.EntityKey = Session.CreateEntityKey("Students", entity);
4 object s=new Student();
5 if (Session.TryGetObjectByKey(entity.EntityKey, out s))
6 {
7 Session.ObjectStateManager.ChangeObjectState(s, System.Data.EntityState.Deleted);
8 Session.Detach(s);
9 }
10 Session.Attach(entity);
11 Session.ObjectStateManager.ChangeObjectState(entity, System.Data.EntityState.Modified);
12 Session.SaveChanges();
13
}
2 {
3 entity.EntityKey = Session.CreateEntityKey("Students", entity);
4 object s=new Student();
5 if (Session.TryGetObjectByKey(entity.EntityKey, out s))
6 {
7 Session.ObjectStateManager.ChangeObjectState(s, System.Data.EntityState.Deleted);
8 Session.Detach(s);
9 }
10 Session.Attach(entity);
11 Session.ObjectStateManager.ChangeObjectState(entity, System.Data.EntityState.Modified);
12 Session.SaveChanges();
13
public void Delete(Student entity)
{
entity.EntityKey = Session.CreateEntityKey("Students", entity);
object s = new Student();
if (Session.TryGetObjectByKey(entity.EntityKey, out s))
{
Session.Students.DeleteObject((Student)s);
}
else
{
Session.AttachTo("Students", entity);
Session.Students.DeleteObject(entity);
}
Session.SaveChanges();
}
{
entity.EntityKey = Session.CreateEntityKey("Students", entity);
object s = new Student();
if (Session.TryGetObjectByKey(entity.EntityKey, out s))
{
Session.Students.DeleteObject((Student)s);
}
else
{
Session.AttachTo("Students", entity);
Session.Students.DeleteObject(entity);
}
Session.SaveChanges();
}
此代码可能存在着各种漏洞。
本文将使用C#来获取系统的基本信息。
结果如图所示：
为了获取系统信息，我将调用windows自带的kernel32.dll程序。代码如下所示：
1 using System;
2 using System.Collections.Generic;
3 using System.ComponentModel;
4 using System.Data;
5 using System.Drawing;
6 using System.Linq;
7 using System.Text;
8 using System.Windows.Forms;
9 using System.Runtime.InteropServices;
10
11 namespace getSystemInfo
12 {
13
14
15 public partial class Form1 : Form
16 {
17 public Form1()
18 {
19 InitializeComponent();
20 }
21
22 [DllImport("kernel32")]
23 public static extern void GetWindowsDirectory(StringBuilder WinDir, int count);
24
25 [DllImport("kernel32")]
26 public static extern void GetSystemDirectory(StringBuilder SysDir, int count);
27
28 [DllImport("kernel32")]
29 public static extern void GetSystemInfo(ref CPU_INFO cpuinfo);
30
31 [DllImport("kernel32")]
32 public static extern void GlobalMemoryStatus(ref MEMORY_INFO meminfo);
33
34 [DllImport("kernel32")]
35 public static extern void GetSystemTime(ref SYSTEMTIME_INFO stinfo);
36
37 //定义以下各结构
38 //定义CPU的信息结构
39 [StructLayout(LayoutKind.Sequential)]
40 public struct CPU_INFO
41 {
42 public uint dwOemId;
43 public uint dwPageSize;
44 public uint lpMinimumApplicationAddress;
45 public uint lpMaximumApplicationAddress;
46 public uint dwActiveProcessorMask;
47 public uint dwNumberOfProcessors;
48 public uint dwProcessorType;
49 public uint dwAllocationGranularity;
50 public uint dwProcessorLevel;
51 public uint dwProcessorRevision;
52 }
53
54 //定义内存的信息结构
55 [StructLayout(LayoutKind.Sequential)]
56 public struct MEMORY_INFO
57 {
58 public uint dwLength;
59 public uint dwMemoryLoad;
60 public uint dwTotalPhys;
61 public uint dwAvailPhys;
62 public uint dwTotalPageFile;
63 public uint dwAvailPageFile;
64 public uint dwTotalVirtual;
65 public uint dwAvailVirtual;
66 }
67
68 //定义系统时间的信息结构
69 [StructLayout(LayoutKind.Sequential)]
70 public struct SYSTEMTIME_INFO
71 {
72 public ushort wYear;
73 public ushort wMonth;
74 public ushort wDayOfWeek;
75 public ushort wDay;
76 public ushort wHour;
77 public ushort wMinute;
78 public ushort wSecond;
79 public ushort wMilliseconds;
80 }
81
82 private void button1_Click(object sender, EventArgs e)
83 {
84 string strResult = null;
85 //调用GetWindowsDirectory和GetSystemDirectory函数分别取得Windows路径和系统路径
86 const int nChars = 128;
87 StringBuilder Buff = new StringBuilder(nChars);
88 GetWindowsDirectory(Buff, nChars);
89 labWindowPath.Text = "Windows路径：" + Buff.ToString();
90 GetSystemDirectory(Buff, nChars);
91 lbSystemPath.Text = "系统路径：" + Buff.ToString();
92
93 //调用GetSystemInfo函数获取CPU的相关信息
94 CPU_INFO CpuInfo;
95 CpuInfo = new CPU_INFO();
96 GetSystemInfo(ref CpuInfo);
97 lbCupCount.Text = "本计算机中有" + CpuInfo.dwNumberOfProcessors.ToString() + "个CPU";
98 lbCpuType.Text = "CPU的类型为" + CpuInfo.dwProcessorType.ToString();
99 strResult += "CPU等级为" + CpuInfo.dwProcessorLevel.ToString();
100 lbCpuEom.Text = "CPU的OEM ID为" + CpuInfo.dwOemId.ToString();
101 strResult += "CPU中的页面大小为" + CpuInfo.dwPageSize.ToString();
102
103 //调用GlobalMemoryStatus函数获取内存的相关信息
104 MEMORY_INFO MemInfo;
105 MemInfo = new MEMORY_INFO();
106 GlobalMemoryStatus(ref MemInfo);
107 lbNcsyl.Text = MemInfo.dwMemoryLoad.ToString() + "%的内存正在使用";
108 LbNCTotal.Text = "物理内存共有" + MemInfo.dwTotalPhys.ToString() + "字节";
109 LbNcKy.Text = "可使用的物理内存有" + MemInfo.dwAvailPhys.ToString() + "字节";
110 strResult += "交换文件总大小为" + MemInfo.dwTotalPageFile.ToString() + "字节";
111 strResult += "尚可交换文件大小为" + MemInfo.dwAvailPageFile.ToString() + "字节";
112 LbXnncTotal.Text = "总虚拟内存有" + MemInfo.dwTotalVirtual.ToString() + "字节";
113 LbKyxnnc.Text = "未用虚拟内存有" + MemInfo.dwAvailVirtual.ToString() + "字节";
114
115 //调用GetSystemTime函数获取系统时间信息
116 SYSTEMTIME_INFO StInfo;
117 StInfo = new SYSTEMTIME_INFO();
118 GetSystemTime(ref StInfo);
119 LabRq.Text = StInfo.wYear.ToString() + "年" + StInfo.wMonth.ToString() + "月" + StInfo.wDay.ToString() + "日";
120 lbXtrq.Text = (StInfo.wHour + 8).ToString() + "点" + StInfo.wMinute.ToString() + "分" + StInfo.wSecond.ToString() + "秒";
121 // label1.Text = strResult.ToString();
122
123 //获取计算机名称
124 lbCompName.Text += System.Environment.UserName;
125 lbMaName.Text += System.Environment.MachineName;
126 lbOSInfo.Text += System.Environment.OSVersion;
127 lbNetName.Text += System.Environment.UserDomainName;
128 }
129 }
130 }
131
Extjs动态加载树，首先在数据库里面设计存放树信息的表
1 USE [KimiExtjs] 2 GO 3 /****** 对象: Table [dbo].[Trees] 脚本日期: 04/08/2010 22:12:25 ******/ 4 SET ANSI_NULLS ON 5 GO 6 SET QUOTED_IDENTIFIER ON 7 GO 8 SET ANSI_PADDING ON 9 GO 10 CREATE TABLE [dbo].[Trees]( 11 [Tid] [varchar](40) COLLATE Chinese_PRC_CI_AS NOT NULL,---节点ID 主键 Guid 12 [ParentId] [varchar](40) COLLATE Chinese_PRC_CI_AS NULL,---父亲节点ID 0表示为根目录 13 [ContentText] [varchar](800) COLLATE Chinese_PRC_CI_AS NULL,---节点现实内容 14 [StrHref] [varchar](800) COLLATE Chinese_PRC_CI_AS NULL,---节点链接地址 15 [hrefTarget] [varchar](50) COLLATE Chinese_PRC_CI_AS NULL,---Target 16 CONSTRAINT [PK_Trees] PRIMARY KEY CLUSTERED 17 ( 18 [Tid] ASC 19 )WITH (IGNORE_DUP_KEY = OFF) ON [PRIMARY] 20 ) ON [PRIMARY] 21 22 GO 23 SET ANSI_PADDING OFF
构建完数据表后，我们将开始应运程序的开发，首先页面的设计，html代码如下：
1 <%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Main.aspx.cs" Inherits="Com.KimiYang.Web.Main" %>
2
3 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
4
5 <html xmlns="http://www.w3.org/1999/xhtml">
6 <head id="Head1" runat="server">
7 <title>无标题页</title>
8 <link href="css/css/StyleSheet.css" rel="stylesheet" type="text/css" />
9
10 <link href="Extjs3.2.0/resources/css/ext-all.css" rel="stylesheet" type="text/css" />
11 <link href="Extjs3.2.0/resources/css/xtheme-gray.css" rel="stylesheet" type="text/css" />
12 <script src="Extjs3.2.0/adapter/ext/ext-base.js" type="text/javascript"></script>
13 <script src="Extjs3.2.0/ext-all.js" type="text/javascript"></script>
14 <script src="Extjs3.2.0/src/locale/ext-lang-zh_CN.js" type="text/javascript"></script>
15
16 <script src="JS/Main.js" type="text/javascript"></script>
17 <script src="JS/NowTime.js" type="text/javascript"></script>
18 <base target="_self" />
19 </head>
20 <body onload="getCurrentTime()">
21 <form id="form1" runat="server">
22 <div id="loading-mask" style=""></div>
23 <div id="loading">
24 <div class="loading-indicator"><img src="Extjs3.2.0/resources/images/vista/s.gif" width="32" height="32" style="margin-right:8px;" align="absmiddle"/>Loading...</div>
25 </div>
26 <div id="header"><h1>KimiYang</h1></div>
27 <div class="menu">
28 <span style="float: left">欢迎 <b>admin <span id="myTime"/></span></b>
29 </span>
30 <span id="aLoginOut" runat="server" style="float: right"><a onclick="if (!window.confirm('您确认要注消当前登录用户吗？')){return false;}"
31 href="#">注销</a></span>
32 </div>
33 <div id="north"></div>
34 <div id="west">
35
36 </div>
37 <div id="center">
38
39 </div>
40 <div id="west_content" style="height:300px; ">
41
42 </div>
43 </form>
44 </body>
45 </html>
46
js代码如下所示:
1 Ext.onReady(function(){
2 Ext.BLANK_IMAGE_URL="Extjs3.2.0/resources/images/default/s.gif";
3 var Tree = Ext.tree;
4 var tree = new Tree.TreePanel({
5 el:'west_content',//渲染到
6 useArrows:true,
7 autoHeight:true,
8 split:true,
9 lines:true,
10 autoScroll:true,
11 animate:true,
12 enableDD:true,
13 border:false,
14 containerScroll: true,
15 loader: new Tree.TreeLoader({
16 dataUrl:'ServletHandlers/GetTrees.ashx'
17 })
18 });
19 var root = new Tree.AsyncTreeNode({
20 text: 'KimiYang',
21 draggable:true,
22 id:'0'
23 });
24 tree.setRootNode(root);
25 tree.render();
26 root.expand();
27
28 var viewport = new Ext.Viewport({
29 layout:'border',
30 items:[{
31 region:'west',
32 id:'west',
33 title:'菜单导航',
34 split:true,
35 width: 200,
36 minSize: 200,
37 maxSize: 400,
38 collapsible: true,
39 margins:'60 0 2 2',
40 cmargins:'60 5 2 2',
41 layout:'fit',
42 layoutConfig:{ activeontop:true},
43 defaults: { bodyStyle: 'margin:0;padding:0;'},
44 items:
45 new Ext.TabPanel({
46 border:false,
47 activeTab:0,
48 tabPosition:'bottom',
49 items:[{
50 contentEl:'west_content',
51 title:'系统管理',
52 autoScroll:true,
53 bodyStyle:'padding:5px;'
54 },
55 {
56 title:'网上办公',
57 autoScroll:true,
58 bodyStyle:'padding:5px;'
59 }]
60 })
61 },{
62 region:'center',
63 el:'center',
64 deferredRender:false,
65 margins:'60 0 2 0',
66 html:'<iframe id="center-iframe" width="100%" height=100% name="main" frameborder="0" scrolling="auto" style="border:0px none; background-color:#BBBBBB; " ></iframe>',
67 autoScroll:true
68 },
69 {
70 region:'south',
71 margins:'0 0 0 2',
72 border:false,
73 html:'<div class="menu south">Copyright © 2009 浙江新昌 Kimi Yang All Rights Reserved</div>'
74 }
75 ]
76 });
77
78 setTimeout(function(){
79 Ext.get('loading').remove();
80 Ext.get('loading-mask').fadeOut({remove:true});
81 }, 250)
82 });
C#代码如下图所示:
1 using System;
2 using System.Collections;
3 using System.Data;
4 using System.Linq;
5 using System.Web;
6 using System.Web.Services;
7 using System.Web.Services.Protocols;
8 using System.Xml.Linq;
9
10 namespace Com.KimiYang.Web.ServletHandlers
11 {
12 /// <summary>
13 /// $codebehindclassname$ 的摘要说明
14 /// </summary>
15 [WebService(Namespace = "http://tempuri.org/")]
16 [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
17 public class GetTrees : IHttpHandler
18 {
19
20 public void ProcessRequest(HttpContext context)
21 {
22 string strSql = "select Tid,ParentId,ContentText,StrHref,hrefTarget from Trees";
23 dbOperator db = new dbOperator();
24 DataTable dt = db.Execute(strSql);
25 string strResult = "[";
26 if (dt.Rows.Count > 0)
27 {
28 DataRow[] dr = dt.Select("ParentId='0'");
29 strResult = DtTreeToJson(dt, strResult, dr);
30 }
31 strResult += "]";
32 context.Response.ContentType = "text/plain";
33 context.Response.Write(strResult.ToString());
34 context.Response.End();
35 }
36
37 private static string DtTreeToJson(DataTable dt, string strResult, DataRow[] dr)
38 {
39 if (dr.Length > 0)
40 {
41 for (int i = 0; i < dr.Length; i++)
42 {
43
44 strResult += "{";
45 strResult += "text:'" + dr[i]["ContentText"] + "',";
46 strResult += "id:'" + dr[i]["Tid"] + "',";
47 DataRow[] drChild = dt.Select("ParentId='" + dr[i]["Tid"] + "'");
48 if (drChild.Length > 0)
49 {
50 strResult += "leaf:false,";
51 strResult += "children:[";
52 strResult = DtTreeToJson(dt, strResult, drChild);
53 strResult += "]";
54 }
55 else
56 {
57 strResult += "href:'" + dr[i]["StrHref"] + "',";
58 strResult += "hrefTarget:'" + dr[i]["hrefTarget"] + "',";
59 strResult += "leaf:true";
60 }
61
62 strResult += "}";
63
64 if (i != dr.Length - 1)
65 strResult += ",";
66 }
67 }
68 return strResult;
69 }
70
71 public bool IsReusable
72 {
73 get
74 {
75 return false;
76 }
77 }
78 }
79 }
80
页面效果图：
源代码下载ExtjsTree.rar
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