〈转〉用VS2005.NET进行三层结构应用程序的开发
１.三層之間的關(guān)系：
三層是指：界面顯示層(UI)，業(yè)務(wù)邏輯層(Business)，數(shù)據(jù)操作層(Data Access)
文字描述：
Clients對(duì)UI進(jìn)行操作，UI調(diào)用Business進(jìn)行相應(yīng)的運(yùn)算和處理，Business通過(guò)Data Access對(duì)Data Base進(jìn)行操作。
?優(yōu)點(diǎn)：
1、增加了代碼的重用。Data Access可在多個(gè)項(xiàng)目中公用；Business可在同一項(xiàng)目的不同地方使用（如某個(gè)軟件B/S和C/S部分可以共用一系列的Business組件）。
2、使得軟件的分層更加明晰，便于開(kāi)發(fā)和維護(hù)。美工人員可以很方便地設(shè)計(jì)UI設(shè)計(jì)，并在其中調(diào)用Business給出的接口，而程序開(kāi)發(fā)人員則可以專注的進(jìn)行代碼的編寫(xiě)和功能的實(shí)現(xiàn)。
?
２.Data Access的具體實(shí)現(xiàn)：
DataAgent類型中變量和方法的說(shuō)明：
?
private string m_strConnectionString; //連接字符串
private OleDbConnection m_objConnection; //數(shù)據(jù)庫(kù)連接
?
public DataAgent(string strConnection) //構(gòu)造方法，傳入的參數(shù)為連接字符串
private void OpenDataBase() //打開(kāi)數(shù)據(jù)庫(kù)連接
private void #region CloseDataBase() //關(guān)閉數(shù)據(jù)庫(kù)連接
public DataView GetDataView(string strSqlStat) //根據(jù)傳入的連接字符串返回DataView
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具體實(shí)現(xiàn)代碼如下：?
Code??1public?class?DataAgent
??2
??3?????{
??4
??5?
??6
??7?????????Variables#region?Variables
??8
??9?
?10
?11?????????private?string?m_strConnectionString;
?12
?13?????????private?OleDbConnection?m_objConnection;
?14
?15?
?16
?17?????????#endregion?Variables
?18
?19?
?20
?21?????????Functions#region?Functions
?22
?23?
?24
?25?????????DataAgend#region?DataAgend
?26
?27?????????/**////?<summary>
?28
?29?????????///?Initial?Function
?30
?31?????????///?</summary>
?32
?33?????????///?<param?name="strConnection"></param>
?34
?35?????????public?DataAgent(string?strConnection)
?36
?37?????????{
?38
?39??????????????this.m_strConnectionString?=?strConnection;
?40
?41?????????}
?42
?43?????????#endregion?DataAgend
?44
?45?
?46
?47?????????OpenDataBase#region?OpenDataBase
?48
?49?????????/**////?<summary>
?50
?51?????????///?function?to?open?data?base
?52
?53?????????///?</summary>
?54
?55?????????private?void?OpenDataBase()
?56
?57?????????{
?58
?59??????????????try
?60
?61??????????????{
?62
?63???????????????????this.m_objConnection?=?new?OleDbConnection();
?64
?65???????????????????this.m_objConnection.ConnectionString?=?this.m_strConnectionString;
?66
?67?
?68
?69???????????????????if(this.m_objConnection.State?!=?ConnectionState.Open)
?70
?71???????????????????{
?72
?73???????????????????????this.m_objConnection.Open();
?74
?75???????????????????}
?76
?77??????????????}
?78
?79??????????????catch(Exception?e)
?80
?81??????????????{
?82
?83???????????????????throw?e;
?84
?85??????????????}
?86
?87?????????}
?88
?89?????????#endregion?OpenDataBase
?90
?91?
?92
?93?????????CloseDataBase#region?CloseDataBase
?94
?95?????????/**////?<summary>
?96
?97?????????///?the?function?to?cloase?data?base
?98
?99?????????///?</summary>
100
101?????????private?void?CloseDataBase()
102
103?????????{
104
105??????????????if(this.m_objConnection?!=?null)
106
107??????????????{
108
109???????????????????if(this.m_objConnection.State?==?ConnectionState.Open)
110
111???????????????????{
112
113????????????????????????this.m_objConnection.Close();
114
115???????????????????}
116
117??????????????}
118
119?????????}
120
121?????????#endregion
122
123?
124
125?????????GetDataView#region?GetDataView
126
127?????????/**////?<summary>
128
129?????????///?Execute?the?sql?and?return?the?default?table?view
130
131?????????///?</summary>
132
133?????????///?<param?name="strSelectString">Select?String</param>
134
135?????????///?<returns>DataView?of?the?DataTable</returns>
136
137?????????public?DataView?GetDataView(string?strSqlStat)
138
139?????????{
140
141??????????????try
142
143??????????????{
144
145???????????????????this.OpenDataBase();
146
147???????????????????OleDbDataAdapter?objDataAdapter?=?new?OleDbDataAdapter(strSqlStat.Trim(),this.m_objConnection);
148
149???????????????????DataSet?objDataSet?=?new?DataSet();
150
151??????????????????objDataAdapter.Fill(objDataSet);
152
153???????????????????return?objDataSet.Tables[0].DefaultView;
154
155??????????????}
156
157??????????????catch(Exception?e)
158
159??????????????{
160
161???????????????????throw?e;
162
163??????????????}
164
165??????????????finally
166
167??????????????{
168
169???????????????????this.CloseDataBase();
170
171??????????????}
172
173?????????}
174
175?????????#endregion?GetDataTable
176
177?????????#endregion?Functions
178
179?
180
181?????}
３.Business的具體實(shí)現(xiàn)：
建立名為Base的類，此類作為其他事務(wù)類的基類，其中定義了一個(gè)DataAgent的實(shí)例。其他所有的Business類都從該改類派生。
在該類中添加對(duì)DataAgent的引用，使所有的事務(wù)類都能使用DataAgent中的方法。
?
Base.cs源代碼：
?
Code?1???public?abstract?class?Base
?2
?3?????{
?4
?5?????????DataAgent#region?DataAgent
?6
?7?????????private?DataAgent?m_objDBAgent;
?8
?9?
10
11?????????protected?DataAgent?OleDBAgent
12
13?????????{
14
15??????????????get
16
17??????????????{
18
19???????????????????if(this.m_objDBAgent?==?null)
20
21???????????????????{
22
23???????????????????????this.m_objDBAgent?=?this.CreateAgent();
24
25???????????????????}
26
27???????????????????return?this.m_objDBAgent;
28
29??????????????}
30
31??????????????set
32
33??????????????{
34
35???????????????????this.m_objDBAgent?=?value;
36
37??????????????}
38
39?????????}
40
41?????????#endregion?DataAgent
42
43?
44
45?????????public?Base()
46
47?????????{
48
49?????????}
50
51?
52
53?????????CreateAgent#region?CreateAgent
54
55?????????/**////?<summary>
56
57?????????///?Create?a?new?DataAgent
58
59?????????///?</summary>
60
61?????????///?<returns>the?DataAgent</returns>
62
63?????????private?DataAgent?CreateAgent()
64
65?????????{
66
67??????????????string?strConnection?=?ConfigurationSettings.AppSettings["ConnectionString"];
68
69??????????????return?new?DataAgent(strConnection);
70
71??????????}
72
73?????????#endregion?CreateAgent
74
75????}
?
???? 準(zhǔn)備好了數(shù)據(jù)操作層和事務(wù)層的基類，底下就可以正式地開(kāi)始業(yè)務(wù)邏輯類的開(kāi)發(fā)了，如有一個(gè)顯示新聞的類News,其中包含了一個(gè)GetNewsLsit()的方法，該方法用來(lái)獲取所有的新聞標(biāo)題列表，代碼如下：
?
Code?1public?class?News:?Base
?2
?3?????{
?4
?5?????????public?News?Contact()
?6
?7?????????{
?8
?9?
10
11?????????}
12
13?
14
15?????????public?DataView?GetNewsList()
16
17?????????{
18
19??????????????string?strSql;
20
21??????????????strSql?=?"";
22
23??????????????strSql?+=?"???SELECT?Top?10?NewsId,NewsTitle?";
24
25??????????????strSql?+=?"?????FROM?Tb_News";
26
27??????????????strSql?+=?"????WHERE?NewsEnable?=?1";
28
29??????????????strSql?+=?"?ORDER?BY?NewsId?";
30
31?
32
33??????????????return?base.OleDBAgent.GetDataView(strSql);
34
35?
36
37?????????}
38
39?????}
?
?
由于數(shù)據(jù)庫(kù)結(jié)構(gòu)比較簡(jiǎn)單，在此就不再給出詳細(xì)的表結(jié)構(gòu)。
?
４.UI層對(duì)Business中接口的調(diào)用
首先，在頁(yè)面中添加對(duì)News類的引用。
然后，在頁(yè)面中添加一個(gè)(DataGrid)dgNews用來(lái)顯示新聞列表。
在Page Behind的Page_Load方法中添加如下代碼：
2
3?????????this.dgNews.DataSource?=?objNews.GetNewsList();
4
5????this.dgNews.DataBind();
?
?
?
Code?1?public?abstract?class?Base
?2
?3?????{
?4
?5?????????DataAgent#region?DataAgent
?6
?7?????????private?DataAgent?m_objDBAgent;
?8
?9?
10
11?????????protected?DataAgent?OleDBAgent
12
13?????????{
14
15??????????????get
16
17??????????????{
18
19???????????????????if(this.m_objDBAgent?==?null)
20
21???????????????????{
22
23???????????????????????this.m_objDBAgent?=?this.CreateAgent();
24
25???????????????????}
26
27???????????????????return?this.m_objDBAgent;
28
29??????????????}
30
31??????????????set
32
33??????????????{
34
35???????????????????this.m_objDBAgent?=?value;
36
37??????????????}
38
39?????????}
40
41?????????#endregion?DataAgent
42
43?
44
45?????????public?Base()
46
47?????????{
48
49?????????}
50
51?
52
53?????????CreateAgent#region?CreateAgent
54
55?????????/**////?<summary>
56
57?????????///?Create?a?new?DataAgent
58
59?????????///?</summary>
60
61?????????///?<returns>the?DataAgent</returns>
62
63?????????private?DataAgent?CreateAgent()
64
65?????????{
66
67??????????????string?strConnection?=?ConfigurationSettings.AppSettings["ConnectionString"];
68
69??????????????return?new?DataAgent(strConnection);
70
71??????????}
72
73?????????#endregion?CreateAgent
74
75????}
轉(zhuǎn)載于:https://www.cnblogs.com/KivenSun/articles/1434368.html
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