在c#中实现3层架构

1、在c#中实现3层架构在c#中实现3层架构作者：佚名 文章来源：本站原创 点击数： 37 更新时间：2006-5-24   原版英文文章地址： 介绍这篇文章讨论如何在c中实现3层架构，使用MS Access数据库存储数据。在此，我在3层架构中实现一个小型的可复用的组件保存客户数据。并提供添加，更新，查找客户数据的功能。背景首先，我介绍一些3层架构的理论知识。简单说明：什么是3层架构？3层架构的优点是什么？什么是3层架构？3层架构是一种“客户端服务器”架构，在此架构中用户接口，商业逻辑，数据保存以及数据访问被设计为独立的模块。主要有3个层面，第一层（表现层，GUI层），第二层（商业对象，

2、商业逻辑层），第三层（数据访问层）。这些层可以单独开发，单独测试。为什么要把程序代码分为3层，把用户接口层，商业逻辑层，数据访问层分离有许多的优点。 在快速开发中重用商业逻辑组件，我们已经在系统中实现添加，更新，删除，查找客户数据的组件。这个组件已经开发并且测试通过，我们可以在其他要保存客户数据的项目中使用这个组件。 系统比较容易迁移，商业逻辑层与数据访问层是分离的，修改数据访问层不会影响到商业逻辑层。系统如果从用SQL Server存储数据迁移到用Oracle存储数据，并不需要修改商业逻辑层组件和GUI组件 系统容易修改，假如在商业层有一个小小的修改，我们不需要

3、在用户的机器上重装整个系统。我们只需要更新商业逻辑组件就可以了。 应用程序开发人员可以并行，独立的开发单独的层。 代码 这个组件有3层，第一个层或者称为GUI层用form实现，叫做FrmGUI。第二层或者称为商业逻辑层，叫做BOCustomer，是Bussniess Object Customer的缩写。最后是第三层或者称为数据层，叫做DACustomer，是Data Access Customer的缩写。为了方便我把三个层编译到一个项目中。 用户接口层   下面是用户接口成的一段代码，我只选取了调用商业逻辑层的一部分代码。/This

4、 function get the details from the user via GUI /tier and calls the Add method of business logic layer.private void cmdAdd_Click(object sender, System.EventArgs e)      try                  cus =

5、 new BOCustomer();            cus.cusID=txtID.Text.ToString();            cus.LName = txtLName.Text.ToString();            cus.FName =

6、txtFName.Text.ToString();            cus.Tel= txtTel.Text.ToString();            cus.Address = txtAddress.Text.ToString();            c

7、us.Add();            catch(Exception err)                  MessageBox.Show(err.Message.ToString();       /This function gets the ID from the

8、 user and finds the /customer details and return the details in the form of/a dataset via busniss object layer. Then it loops through /the content of the dataset and fills the controls. private void cmdFind_Click(object sender, System.EventArgs e)      try  &#

9、160;               String cusID = txtID.Text.ToString();                              BOCustome

10、r thisCus = new BOCustomer();                              DataSet ds = thisCus.Find(cusID);           &#

11、160; DataRow row;            row = ds.Tables0.Rows0;             /via looping            foreach(DataRow rows in ds.Tables0.Rows )

12、                           txtFName.Text = rows"CUS_F_NAME".ToString();               txtLName.

13、Text = rows"CUS_L_NAME".ToString();               txtAddress.Text = rows"CUS_ADDRESS".ToString();               txtTel.Text = rows"CUS_

14、TEL".ToString();                       catch (Exception err)                  MessageBox.Show(err.Message.ToString(

15、);        /this function used to update the customer details. private void cmdUpdate_Click(object sender,                           

16、60;      System.EventArgs e)      try                  cus = new BOCustomer();            cus.cusID=txtID.Text.ToSt

17、ring();            cus.LName = txtLName.Text.ToString();            cus.FName = txtFName.Text.ToString();            cus.Tel= txtTel.Te

18、xt.ToString();            cus.Address = txtAddress.Text.ToString();             cus.Update();            catch(Exception err) 

19、0;                MessageBox.Show(err.Message.ToString();      商业逻辑层下面是商业逻辑层的所有代码，主要包括定义customer对象的属性。但这仅仅是个虚构的customer对象，如果需要可以加入其他的属性。商业逻辑层还包括添加，更新，查找，等方法。商业逻辑层是一个中间层，处于GUI层和数据访问层中间。他有一个指向数据访问层的引用cusData

20、 = new DACustomer().而且还引用了System.Data名字空间。商业逻辑层使用DataSet返回数据给GUI层。 using System;using System.Data; namespace _3tierarchitecture      / <SUMMARY>      / Summary description for BOCustomer.      / </SUMMARY&g

21、t;            public class BOCustomer                  /Customer properties            private String fName; &

22、#160;          private String lName;            private String cusId;            private String address;       

23、;     private String tel;             private DACustomer cusData;        public BOCustomer()                &#

24、160;  /An instance of the Data access layer!             cusData = new DACustomer();                           / &l

25、t;SUMMARY>            / Property FirstName (String)            / </SUMMARY>            public String FName    &

26、#160;                                get                    

27、                      return this.fName;                          

28、0;         set                                          try&

29、#160;                                                  

30、   this.fName = value;                               if (this.fName = "")         

31、60;                                                  &#

32、160;     throw new Exception(                                      "Please provide first n

33、ame .");                                                

34、0;                             catch(Exception e)                   &#

35、160;                                  throw new Exception(e.Message.ToString();          &

36、#160;                                                   

37、0;    / <SUMMARY>            / Property LastName (String)            / </SUMMARY>            public String L

38、Name                              get                     &#

39、160;                    return this.lName;                            

40、        set                                          /could be mo

41、re checkings here eg revmove ' chars                        /change to proper case                

42、60;       /blah blah                        this.lName = value;               &#

43、160;        if (this.LName = "")                                      

44、                throw new Exception("Please provide name .");                          

45、60;                                                    

46、 / <SUMMARY>            / Property Customer ID (String)            / </SUMMARY>            public String cusID  &

47、#160;                           get                        &

48、#160;                 return this.cusId;                               

49、;     set                                          this.cusId = value; 

50、0;                      if (this.cusID = "")                        &#

51、160;                             throw new Exception("Please provide ID .");            &#

52、160;                                                    

53、;   / <SUMMARY>            / Property Address (String)            / </SUMMARY>            public String Address&#

54、160;                             get                      &#

55、160;                   return this.address;                            

56、0;       set                                          this.address = v

57、alue;                         if (this.Address = "")                   

58、0;                                  throw new Exception("Please provide address .");       

59、0;                                                    &

60、#160;      / <SUMMARY>            / Property Telephone (String)            / </SUMMARY>           

61、 public String Tel                              get                   

62、                       return this.tel;                          

63、          set                                         

64、this.tel = value;                        if (this.Tel = "")                   &#

65、160;                                  throw new Exception("Please provide Tel .");        

66、                                                    

67、60;       / <SUMMARY>            / Function Add new customer. Calls             / the function in Data layer.       

68、60;    / </SUMMARY>            public void Add()                              cusDat

69、a.Add(this);                          / <SUMMARY>            / Function Update customer details.    

70、0;        / Calls the function in Data layer.            / </SUMMARY>            public void Update()         

71、;                      cusData.Update(this);                         / <SUMMARY>

72、;            / Function Find customer. Calls the             / function in Data layer.            / It returns the details of the custo

73、mer using             / customer ID via a Dataset to GUI tier.            / </SUMMARY>            public DataSet Find(String str)

74、                               if (str = "")                 

75、0;    throw new Exception("Please provide ID to search");                                     &

76、#160;  DataSet data = null;                   data = cusData.Find(str);                   return data;  &

77、#160;                数据访问层 数据层包括处理MS Access数据库的细节。所有这些细节都是透明的，不会影响到商业逻辑层。数据访问层有个指向商业逻辑层的引用BOCustomer cus。为了应用方便并且支持其他数据库。using System;using System.Data.OleDb;using System.Data; namespace _3tierarchitecture  

78、60;   / <SUMMARY>    / Summary description for DACustomer.    / </SUMMARY>    public class DACustomer            private OleDbConnection cnn;       

79、 /change connection string as per the         /folder you unzip the files        private const string CnnStr =           "Provider=Microsoft.Jet.OLEDB.4.0;Data " +  

80、        "Source= D:Rahman_BackupProgramming" +              "Csharp3tierarchitecturecustomer.mdb;"         /local variables   

81、0;    private String strTable=""        private String strFields=""        private String strValues=""        private String insertStr=""

82、60;               /this needs to be changed based on customer         /table fields' Name of the database!        private const String thisTable = "tblCusto

83、mer"        private const String cus_ID = "CUS_ID"        private const String cus_LName = "CUS_L_NAME"        private const String cus_FName = "CUS_F_NAME"

84、0;       private const String cus_Tel = "CUS_TEL"        private const String cus_Address = "CUS_ADDRESS"          public DACustomer()      

85、                          public DACustomer(BOCustomer cus)                    / A reference of the

86、business object class                        /standard dataset function that adds a new customer         public void Add(BOCustomer cus)   &

87、#160;                 String str = BuildAddString(cus);                        OpenCnn();    &#

88、160;        /Open command option - cnn parameter is imporant            OleDbCommand cmd = new OleDbCommand(str,cnn);              /execute conne

89、ction            cmd.ExecuteNonQuery();                        / close connection         

90、   CloseCnn();                                    /standard dataset function that updates       

91、0; /details of a customer based on ID        public void Update(BOCustomer cus)                    OpenCnn();           

92、             String selectStr = "UPDATE " + thisTable +                 " set " + cus_LName + " = '" + cus.LName + "'" +&#

93、160;               ", " + cus_FName + " = '" + cus.FName + "'" +                ", " + cus_Address + "

94、 = '" + cus.Address + "'" +                ", " + cus_Tel + " = '" + cus.Tel + "'" +             &#

95、160;  " where cus_ID = '" + cus.cusID + "'"             OleDbCommand cmd = new OleDbCommand(selectStr,cnn);             cmd.ExecuteNonQuery(); 

96、;                       CloseCnn();                        /standard dataset function that

97、 finds and         /return the detail of a customer in a dataset        public DataSet Find(String argStr)                    DataSet ds=nul

98、l;             try                            OpenCnn();         

99、                   String selectStr = "select * from " + thisTable +                       

100、0;       " where cus_ID = '" + argStr + "'"                OleDbDataAdapter da =               &#

101、160;        new OleDbDataAdapter(selectStr,cnn);                ds = new DataSet();                da.Fill(ds,thisT

102、able);                            CloseCnn();                     

103、0;                   catch(Exception e)                            String Str = e.Message;