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基于LINQ to SQL的WEB开发三层架构(2)

 2023-09-07 阅读 18 评论 0

摘要：初始的Northwind.dbml文件代码如下： #pragma warning disable 1591 //------------------------------------------------------------------------------ // // 此代码由工具生成。 // 运行时版本:2.0.50727.3053 // // 对此文件的更改可能会导致不正确的行为，

初始的Northwind.dbml文件代码如下：

 

#pragma warning disable 1591
//------------------------------------------------------------------------------
// 
//     此代码由工具生成。
//     运行时版本:2.0.50727.3053
//
//     对此文件的更改可能会导致不正确的行为，并且如果
//     重新生成代码，这些更改将会丢失。
// 
//------------------------------------------------------------------------------
namespace DAL
{
using System.Data.Linq;
using System.Data.Linq.Mapping;
using System.Data;
using System.Collections.Generic;
using System.Reflection;
using System.Linq;
using System.Linq.Expressions;
using System.ComponentModel;
using System;
[System.Data.Linq.Mapping.DatabaseAttribute(Name="Northwind")]
public partial class NorthwindDataContext : System.Data.Linq.DataContext
{
private static System.Data.Linq.Mapping.MappingSource mappingSource = new AttributeMappingSource();
#region Extensibility Method Definitions
partial void OnCreated();
partial void InsertEmployees(Employees instance);
partial void UpdateEmployees(Employees instance);
partial void DeleteEmployees(Employees instance);
#endregion
public NorthwindDataContext() : 
base(global::DAL.Properties.Settings.Default.NorthwindConnectionString, mappingSource){
OnCreated();
}
public NorthwindDataContext(string connection) : 
base(connection, mappingSource)
{
OnCreated();
}
public NorthwindDataContext(System.Data.IDbConnection connection) : base(connection, mappingSource)
{
OnCreated();
}
public NorthwindDataContext(string connection, System.Data.Linq.Mapping.MappingSource mappingSource) : 
base(connection, mappingSource)
{
OnCreated();
}
public NorthwindDataContext(System.Data.IDbConnection connection, System.Data.Linq.Mapping.MappingSource mappingSource) : 
base(connection, mappingSource)
{
OnCreated();
}
public System.Data.Linq.Table Employees
{
get
{
return this.GetTable();
}
}
}
[Table(Name="dbo.Employees")]
public partial class Employees : INotifyPropertyChanging, INotifyPropertyChanged
{
private static PropertyChangingEventArgs emptyChangingEventArgs = new PropertyChangingEventArgs(String.Empty);
private int _EmployeeID;
private string _LastName;
private string _FirstName;
private string _Title;
private string _TitleOfCourtesy;
private System.Nullable _BirthDate;
private System.Nullable _HireDate;
private string _Address;
private string _City;
private string _Region;
private string _PostalCode;
private string _Country;
private string _HomePhone;
private string _Extension;
private System.Data.Linq.Binary _Photo;
private string _Notes;
private System.Nullable _ReportsTo;
private string _PhotoPath;
#region Extensibility Method Definitions
partial void OnLoaded();
partial void OnValidate(System.Data.Linq.ChangeAction action);
partial void OnCreated();
partial void OnEmployeeIDChanging(int value);
partial void OnEmployeeIDChanged();
partial void OnLastNameChanging(string value);
partial void OnLastNameChanged();
partial void OnFirstNameChanging(string value);
partial void OnFirstNameChanged();
partial void OnTitleChanging(string value);
partial void OnTitleChanged();
partial void OnTitleOfCourtesyChanging(string value);
partial void OnTitleOfCourtesyChanged();
partial void OnBirthDateChanging(System.Nullable value);
partial void OnBirthDateChanged();
partial void OnHireDateChanging(System.Nullable value);
partial void OnHireDateChanged();
partial void OnAddressChanging(string value);
partial void OnAddressChanged();
partial void OnCityChanging(string value);
partial void OnCityChanged();
partial void OnRegionChanging(string value);
partial void OnRegionChanged();
partial void OnPostalCodeChanging(string value);
partial void OnPostalCodeChanged();
partial void OnCountryChanging(string value);
partial void OnCountryChanged();
partial void OnHomePhoneChanging(string value);
partial void OnHomePhoneChanged();
partial void OnExtensionChanging(string value);
partial void OnExtensionChanged();
partial void OnPhotoChanging(System.Data.Linq.Binary value);
partial void OnPhotoChanged();
partial void OnNotesChanging(string value);
partial void OnNotesChanged();
partial void OnReportsToChanging(System.Nullable value);
partial void OnReportsToChanged();
partial void OnPhotoPathChanging(string value);
partial void OnPhotoPathChanged();
#endregion
public Employees(){
OnCreated();
}
[Column(Storage="_EmployeeID", DbType="Int NOT NULL", IsPrimaryKey=true)]
public int EmployeeID
{
get
{
return this._EmployeeID;
}
set
{
if ((this._EmployeeID != value))
{
this.OnEmployeeIDChanging(value);
this.SendPropertyChanging();
this._EmployeeID = value;
this.SendPropertyChanged("EmployeeID");
this.OnEmployeeIDChanged();
}}
}
[Column(Storage="_LastName", DbType="NVarChar(20) NOT NULL", CanBeNull=false)]
public string LastName
{
get
{
return this._LastName;
}
set
{
if ((this._LastName != value))
{
this.OnLastNameChanging(value);
this.SendPropertyChanging();
this._LastName = value;
this.SendPropertyChanged("LastName");
this.OnLastNameChanged();
}
}
}
[Column(Storage="_FirstName", DbType="NVarChar(10) NOT NULL", CanBeNull=false)]
public string FirstName
{
get
{
return this._FirstName;
}set
{
if ((this._FirstName != value))
{
this.OnFirstNameChanging(value);
this.SendPropertyChanging();
this._FirstName = value;
this.SendPropertyChanged("FirstName");
this.OnFirstNameChanged();
}
}
}
[Column(Storage="_Title", DbType="NVarChar(30)")]
public string Title
{
get
{
return this._Title;
}
set
{
if ((this._Title != value))
{
this.OnTitleChanging(value);
this.SendPropertyChanging();
this._Title = value;
this.SendPropertyChanged("Title");
this.OnTitleChanged();
}
}
}
[Column(Storage="_TitleOfCourtesy", DbType="NVarChar(25)")]
public string TitleOfCourtesy
{
get
{
return this._TitleOfCourtesy;
}
set
{
if ((this._TitleOfCourtesy != value))
{
this.OnTitleOfCourtesyChanging(value);
this.SendPropertyChanging();
this._TitleOfCourtesy = value;
this.SendPropertyChanged("TitleOfCourtesy");
this.OnTitleOfCourtesyChanged();
}
}
}
[Column(Storage="_BirthDate", DbType="DateTime")]
public System.Nullable BirthDate
{
get
{
return this._BirthDate;
}
set
{
if ((this._BirthDate != value))
{
this.OnBirthDateChanging(value);
this.SendPropertyChanging();
this._BirthDate = value;
this.SendPropertyChanged("BirthDate");
this.OnBirthDateChanged();
}}
}
[Column(Storage="_HireDate", DbType="DateTime")]
public System.Nullable HireDate
{
get
{
return this._HireDate;
}
set
{
if ((this._HireDate != value))
{
this.OnHireDateChanging(value);
this.SendPropertyChanging();
this._HireDate = value;
this.SendPropertyChanged("HireDate");
this.OnHireDateChanged();
}
}
}
[Column(Storage="_Address", DbType="NVarChar(60)")]
public string Address
{
get
{
return this._Address;
}
set
{
if ((this._Address != value))
{
this.OnAddressChanging(value);
this.SendPropertyChanging();
this._Address = value;
this.SendPropertyChanged("Address");
this.OnAddressChanged();
}
}}
[Column(Storage="_City", DbType="NVarChar(15)")]
public string City
{
get
{
return this._City;
}
set
{
if ((this._City != value))
{
this.OnCityChanging(value);
this.SendPropertyChanging();
this._City = value;
this.SendPropertyChanged("City");
this.OnCityChanged();
}
}
}[Column(Storage="_Region", DbType="NVarChar(15)")]
public string Region
{
get
{
return this._Region;
}
set
{
if ((this._Region != value))
{
this.OnRegionChanging(value);
this.SendPropertyChanging();
this._Region = value;
this.SendPropertyChanged("Region");
this.OnRegionChanged();
}
}
}
[Column(Storage="_PostalCode", DbType="NVarChar(10)")]
public string PostalCode
{
get
{
return this._PostalCode;
}set
{
if ((this._PostalCode != value))
{
this.OnPostalCodeChanging(value);
this.SendPropertyChanging();
this._PostalCode = value;
this.SendPropertyChanged("PostalCode");
this.OnPostalCodeChanged();
}
}
}
[Column(Storage="_Country", DbType="NVarChar(15)")]
public string Country
{
get
{
return this._Country;
}
set
{
if ((this._Country != value))
{
this.OnCountryChanging(value);
this.SendPropertyChanging();
this._Country = value;
this.SendPropertyChanged("Country");
this.OnCountryChanged();
}
}}
[Column(Storage="_HomePhone", DbType="NVarChar(24)")]
public string HomePhone
{
get
{
return this._HomePhone;
}set
{
if ((this._HomePhone != value))
{
this.OnHomePhoneChanging(value);
this.SendPropertyChanging();
this._HomePhone = value;
this.SendPropertyChanged("HomePhone");
this.OnHomePhoneChanged();
}
}
}
[Column(Storage="_Extension", DbType="NVarChar(4)")]
public string Extension
{
get
{
return this._Extension;
}
set
{
if ((this._Extension != value))
{
this.OnExtensionChanging(value);
this.SendPropertyChanging();
this._Extension = value;
this.SendPropertyChanged("Extension");
this.OnExtensionChanged();
}}
}
[Column(Storage="_Photo", DbType="Image", UpdateCheck=UpdateCheck.Never)]
public System.Data.Linq.Binary Photo
{
get
{
return this._Photo;
}
set
{
if ((this._Photo != value))
{
this.OnPhotoChanging(value);
this.SendPropertyChanging();
this._Photo = value;
this.SendPropertyChanged("Photo");
this.OnPhotoChanged();
}
}
}
[Column(Storage="_Notes", DbType="NText", UpdateCheck=UpdateCheck.Never)]
public string Notes
{
get
{
return this._Notes;
}
set
{
if ((this._Notes != value))
{
this.OnNotesChanging(value);
this.SendPropertyChanging();
this._Notes = value;
this.SendPropertyChanged("Notes");
this.OnNotesChanged();
}
}
}
[Column(Storage="_ReportsTo", DbType="Int")]
public System.Nullable ReportsTo
{
get
{
return this._ReportsTo;
}
set
{
if ((this._ReportsTo != value))
{
this.OnReportsToChanging(value);
this.SendPropertyChanging();
this._ReportsTo = value;
this.SendPropertyChanged("ReportsTo");
this.OnReportsToChanged();
}}
}
[Column(Storage="_PhotoPath", DbType="NVarChar(255)")]
public string PhotoPath
{
get
{
return this._PhotoPath;
}set
{
if ((this._PhotoPath != value))
{
this.OnPhotoPathChanging(value);
this.SendPropertyChanging();
this._PhotoPath = value;
this.SendPropertyChanged("PhotoPath");
this.OnPhotoPathChanged();
}
}
}
public event PropertyChangingEventHandler PropertyChanging;
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void SendPropertyChanging()
{
if ((this.PropertyChanging != null))
{
this.PropertyChanging(this, emptyChangingEventArgs);
}
}
protected virtual void SendPropertyChanged(String propertyName)
{
if ((this.PropertyChanged != null))
{
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
}
#pragma warning restore 1591

 

 

从中可以看到，这里本质上就是以前的数据模型层，将数据整个对象化了，为了层之间的访 问方便，我们将改类的命名空间改为Auto.DAL，并将NorthwindDataContent类的第一个构造函 数代码修改如下，这样修改主要是为了统一数据库连接字符串的位置，因为dbml文件在生成后 会附带生成一个app.config文件，用来存放连接字符串，而我们要把连接字符串统一放到 web.config中。（要访问web.config文件，需要为DAL项目添加对System.Configuration的应用 ）

public NorthwindDataContext() :
base
(ConfigurationManager.ConnectionStrings
["NorthwindConnectionString"].ConnectionString, mappingSource)
{
OnCreated
();
}
完成前面的操作以后，开始建立数据访问层的类文件，这时，先在 DAL项目下添加一个类文件，取名为DALEmployees.cs，其代码如下：

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Auto.DAL
{
public class DALEmployees
{
/// 
/// VS自动生成的数据模型
/// 
NorthwindDataContext db = new NorthwindDataContext();
/// 
/// 根据条件获取数据列表方法
/// 
/// 城 市地址
/// 获取的Employees数据列表
public IQueryable GetList(string strCity)
{
//根据城市地质，通过LINQ返 回数据
return from p in db.Employees
where p.City == strCity
select p;
}
}
}

 

 

这个数据访问层中只建立了一个用来根据城市地址获取Employee数据的方法，它内部执行一 段LINQ，返回一个IQueryable型的结果，由于LINQ后期编译的特性，这个结果只有在程序运行 后才会返回数据集。

接着，建立业务逻辑层，在BLL项目中，添加一个类文件，取名为BLLEmployees.cs，其代码 如下：

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Auto.DAL;
namespace Auto.BLL
{
public class BLLEmployees
{
/// 
/// 通过城市名获得Employee数据
/// 
/// 城市名
/// 数据 结果
public IQueryable GetList(string strCity)
{ 
DALEmployees de=new DALEmployees();
//调用数据访问层的方法
return de.GetList(strCity);
}
}
}

 

这段代码完成了业务逻辑层的定义，建立了一个和数据访问层的同名方法GetList，用来传 送城市名称参数。最后，在WEB Application项目中，添加对BLL层的应用，并在Default.aspx 页面中添加一个GridView控件用来显示数据，Default.aspx.cs的代码如下：

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using Auto.BLL;
namespace WebApplication2
{
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
GetList("London");
}} 
/// 
/// 根据城市获取数据
/// 
/// 城市名称
private void GetList(string strCity) 
{
//执行业务逻辑层的方法
BLLEmployees bl = new BLLEmployees();
//绑 定到GridView1控件
GridView1.DataSource = bl.GetList (strCity);
GridView1.DataBind();
}}}
 

完成后，执行程序，便可得到相关数据，整个程序的结构如下：

总结：实际上，这个基于LINQ的架构是将数据模型层和数据访问层整合到一个项目中，它的 特点就是开发快速，效率高，可以很方便的帮你完成数据模型的搭建，并且也便于后期修改， 当数据表发生变动时，只选要修改dbml文件就可以了。但这个架构里有些地方还是不大完善， 例如城市数据作为参数，应该也是以数据模型的方式来传送，但这里仅是按字符串传递，这样 不利于数据的封装和安全。因此还需要在此处改进。总体来说，比以往的三层架构结构更加清 晰了，如果再结合ASP.NET MVC架构来使用，就更加完美了。

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原文链接：https://hbdhgg.com/4/11380.html

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