在前面的文章中我们提到Entity Framework的“Code First”模式也同样可以基于现有数据库进行开发。今天就让我们一起看一下使用Entity Framework Power Tools如何基于现有数据库生成数据类和数据库上下等。

Entity Framework Power Tools

基于现有数据库生成POCO数据类和数据库上下文需要借助Visual Studio一个扩展插件-- Entity Framework Power Tools（一个Code First反向工程工具）。只要在Visual Studio扩展里面输入“Entity Framework Power”搜索即可找到最新的扩展，点击下载即可（如下图）。当然你也可以到这里Entity Framework Power Tools Beta 3下载安装包进行安装。

安装完之后只要在项目上右键选择Entity Framework->Reverse Engineer Code First（项目中首先需要安装Entity Framework 包，否则会有错误），然后在弹出的窗口中输入相关的数据库连接信息即可（我们这里使用“AdventureWorks”数据库）。

注意：如果使用“AdventureWorks”数据库，可能发生如下错误： One or more errors occurred while loading schema information. error 6004: The table 'AdventureWorks.Production.Document' is referenced by a relationship, but cannot be found. 这是由于EF目前还不支持SQL Server 2008中新增的“Hierarchyid”数据类型，目前只有先不用该类型的数据了，暂时将它改为其他类型。

然后我们稍等片刻，可以看到Entity Framework Power Tools已经根据所选数据库自动为你生成了数据类、数据库上下文操作类、对应的映射配置类并添加了数据库连接配置。

我们先看一下配置文件，可以看到在配置文件中Entity Framework Power Tools已经自动对数据库连接串进行了配置，添加了名为“AdventureWorksContext”的数据库连接串：

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <configSections>
    <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 -->
    <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=5.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
  </configSections>
  <connectionStrings>
    <add name="AdventureWorksContext" connectionString="Data Source=.\SQL2008;Initial Catalog=AdventureWorks;Persist Security Info=True;User ID=sa;Password=123;MultipleActiveResultSets=True"
      providerName="System.Data.SqlClient" />
  </connectionStrings>
  <startup>
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
  </startup>
  <entityFramework>
    <defaultConnectionFactory type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework">
      <parameters>
        <parameter value="v11.0" />
      </parameters>
    </defaultConnectionFactory>
  </entityFramework>
</configuration>

与此同时，对生成的数据库上下文操作类“AdventureWorksContext”进行了配置，在构造函数中使用了上面配置的“AdventureWorksContext”数据库连接：

using System.Data.Entity;
using System.Data.Entity.Infrastructure;
using EFPowerTools.Models.Mapping;

namespace EFPowerTools.Models
{
    public partial class AdventureWorksContext : DbContext
    {
        static AdventureWorksContext()
        {
            Database.SetInitializer<AdventureWorksContext>(null);
        }

        public AdventureWorksContext()
            : base("Name=AdventureWorksContext")
        {
        }

        public DbSet<AWBuildVersion> AWBuildVersions { get; set; }
        public DbSet<DatabaseLog> DatabaseLogs { get; set; }
        public DbSet<ErrorLog> ErrorLogs { get; set; }
        public DbSet<OrderDetail> OrderDetails { get; set; }
        public DbSet<Order> Orders { get; set; }
        public DbSet<Department> Departments { get; set; }
        public DbSet<Employee> Employees { get; set; }
        public DbSet<EmployeeDepartmentHistory> EmployeeDepartmentHistories { get; set; }
        public DbSet<EmployeePayHistory> EmployeePayHistories { get; set; }
        public DbSet<JobCandidate> JobCandidates { get; set; }
        public DbSet<Shift> Shifts { get; set; }
        public DbSet<Address> Addresses { get; set; }
        public DbSet<AddressType> AddressTypes { get; set; }
        public DbSet<BusinessEntity> BusinessEntities { get; set; }
        public DbSet<BusinessEntityAddress> BusinessEntityAddresses { get; set; }
        public DbSet<BusinessEntityContact> BusinessEntityContacts { get; set; }
        public DbSet<ContactType> ContactTypes { get; set; }
        public DbSet<CountryRegion> CountryRegions { get; set; }
        public DbSet<EmailAddress> EmailAddresses { get; set; }
        public DbSet<Password> Passwords { get; set; }
        public DbSet<Person> People { get; set; }
        public DbSet<PersonPhone> PersonPhones { get; set; }
        public DbSet<PhoneNumberType> PhoneNumberTypes { get; set; }
        public DbSet<StateProvince> StateProvinces { get; set; }
        public DbSet<BillOfMaterial> BillOfMaterials { get; set; }
        public DbSet<Culture> Cultures { get; set; }
        public DbSet<Illustration> Illustrations { get; set; }
        public DbSet<Location> Locations { get; set; }
        public DbSet<Product> Products { get; set; }
        public DbSet<ProductCategory> ProductCategories { get; set; }
        public DbSet<ProductCostHistory> ProductCostHistories { get; set; }
        public DbSet<ProductDescription> ProductDescriptions { get; set; }
        public DbSet<ProductInventory> ProductInventories { get; set; }
        public DbSet<ProductListPriceHistory> ProductListPriceHistories { get; set; }
        public DbSet<ProductModel> ProductModels { get; set; }
        public DbSet<ProductModelIllustration> ProductModelIllustrations { get; set; }
        public DbSet<ProductModelProductDescriptionCulture> ProductModelProductDescriptionCultures { get; set; }
        public DbSet<ProductPhoto> ProductPhotoes { get; set; }
        public DbSet<ProductProductPhoto> ProductProductPhotoes { get; set; }
        public DbSet<ProductReview> ProductReviews { get; set; }
        public DbSet<ProductSubcategory> ProductSubcategories { get; set; }
        public DbSet<ScrapReason> ScrapReasons { get; set; }
        public DbSet<TransactionHistory> TransactionHistories { get; set; }
        public DbSet<TransactionHistoryArchive> TransactionHistoryArchives { get; set; }
        public DbSet<UnitMeasure> UnitMeasures { get; set; }
        public DbSet<WorkOrder> WorkOrders { get; set; }
        public DbSet<WorkOrderRouting> WorkOrderRoutings { get; set; }
        public DbSet<ProductVendor> ProductVendors { get; set; }
        public DbSet<PurchaseOrderDetail> PurchaseOrderDetails { get; set; }
        public DbSet<PurchaseOrderHeader> PurchaseOrderHeaders { get; set; }
        public DbSet<ShipMethod> ShipMethods { get; set; }
        public DbSet<Vendor> Vendors { get; set; }
        public DbSet<CountryRegionCurrency> CountryRegionCurrencies { get; set; }
        public DbSet<CreditCard> CreditCards { get; set; }
        public DbSet<Currency> Currencies { get; set; }
        public DbSet<CurrencyRate> CurrencyRates { get; set; }
        public DbSet<Customer> Customers { get; set; }
        public DbSet<PersonCreditCard> PersonCreditCards { get; set; }
        public DbSet<SalesOrderDetail> SalesOrderDetails { get; set; }
        public DbSet<SalesOrderHeader> SalesOrderHeaders { get; set; }
        public DbSet<SalesOrderHeaderSalesReason> SalesOrderHeaderSalesReasons { get; set; }
        public DbSet<SalesPerson> SalesPersons { get; set; }
        public DbSet<SalesPersonQuotaHistory> SalesPersonQuotaHistories { get; set; }
        public DbSet<SalesReason> SalesReasons { get; set; }
        public DbSet<SalesTaxRate> SalesTaxRates { get; set; }
        public DbSet<SalesTerritory> SalesTerritories { get; set; }
        public DbSet<SalesTerritoryHistory> SalesTerritoryHistories { get; set; }
        public DbSet<ShoppingCartItem> ShoppingCartItems { get; set; }
        public DbSet<SpecialOffer> SpecialOffers { get; set; }
        public DbSet<SpecialOfferProduct> SpecialOfferProducts { get; set; }
        public DbSet<Store> Stores { get; set; }
        public DbSet<vEmployee> vEmployees { get; set; }
        public DbSet<vEmployeeDepartment> vEmployeeDepartments { get; set; }
        public DbSet<vEmployeeDepartmentHistory> vEmployeeDepartmentHistories { get; set; }
        public DbSet<vJobCandidate> vJobCandidates { get; set; }
        public DbSet<vJobCandidateEducation> vJobCandidateEducations { get; set; }
        public DbSet<vJobCandidateEmployment> vJobCandidateEmployments { get; set; }
        public DbSet<vAdditionalContactInfo> vAdditionalContactInfoes { get; set; }
        public DbSet<vStateProvinceCountryRegion> vStateProvinceCountryRegions { get; set; }
        public DbSet<vProductAndDescription> vProductAndDescriptions { get; set; }
        public DbSet<vProductModelCatalogDescription> vProductModelCatalogDescriptions { get; set; }
        public DbSet<vProductModelInstruction> vProductModelInstructions { get; set; }
        public DbSet<vVendorWithAddress> vVendorWithAddresses { get; set; }
        public DbSet<vVendorWithContact> vVendorWithContacts { get; set; }
        public DbSet<vIndividualCustomer> vIndividualCustomers { get; set; }
        public DbSet<vPersonDemographic> vPersonDemographics { get; set; }
        public DbSet<vSalesPerson> vSalesPersons { get; set; }
        public DbSet<vSalesPersonSalesByFiscalYear> vSalesPersonSalesByFiscalYears { get; set; }
        public DbSet<vStoreWithAddress> vStoreWithAddresses { get; set; }
        public DbSet<vStoreWithContact> vStoreWithContacts { get; set; }
        public DbSet<vStoreWithDemographic> vStoreWithDemographics { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Configurations.Add(new AWBuildVersionMap());
            modelBuilder.Configurations.Add(new DatabaseLogMap());
            modelBuilder.Configurations.Add(new ErrorLogMap());
            modelBuilder.Configurations.Add(new OrderDetailMap());
            modelBuilder.Configurations.Add(new OrderMap());
            modelBuilder.Configurations.Add(new DepartmentMap());
            modelBuilder.Configurations.Add(new EmployeeMap());
            modelBuilder.Configurations.Add(new EmployeeDepartmentHistoryMap());
            modelBuilder.Configurations.Add(new EmployeePayHistoryMap());
            modelBuilder.Configurations.Add(new JobCandidateMap());
            modelBuilder.Configurations.Add(new ShiftMap());
            modelBuilder.Configurations.Add(new AddressMap());
            modelBuilder.Configurations.Add(new AddressTypeMap());
            modelBuilder.Configurations.Add(new BusinessEntityMap());
            modelBuilder.Configurations.Add(new BusinessEntityAddressMap());
            modelBuilder.Configurations.Add(new BusinessEntityContactMap());
            modelBuilder.Configurations.Add(new ContactTypeMap());
            modelBuilder.Configurations.Add(new CountryRegionMap());
            modelBuilder.Configurations.Add(new EmailAddressMap());
            modelBuilder.Configurations.Add(new PasswordMap());
            modelBuilder.Configurations.Add(new PersonMap());
            modelBuilder.Configurations.Add(new PersonPhoneMap());
            modelBuilder.Configurations.Add(new PhoneNumberTypeMap());
            modelBuilder.Configurations.Add(new StateProvinceMap());
            modelBuilder.Configurations.Add(new BillOfMaterialMap());
            modelBuilder.Configurations.Add(new CultureMap());
            modelBuilder.Configurations.Add(new IllustrationMap());
            modelBuilder.Configurations.Add(new LocationMap());
            modelBuilder.Configurations.Add(new ProductMap());
            modelBuilder.Configurations.Add(new ProductCategoryMap());
            modelBuilder.Configurations.Add(new ProductCostHistoryMap());
            modelBuilder.Configurations.Add(new ProductDescriptionMap());
            modelBuilder.Configurations.Add(new ProductInventoryMap());
            modelBuilder.Configurations.Add(new ProductListPriceHistoryMap());
            modelBuilder.Configurations.Add(new ProductModelMap());
            modelBuilder.Configurations.Add(new ProductModelIllustrationMap());
            modelBuilder.Configurations.Add(new ProductModelProductDescriptionCultureMap());
            modelBuilder.Configurations.Add(new ProductPhotoMap());
            modelBuilder.Configurations.Add(new ProductProductPhotoMap());
            modelBuilder.Configurations.Add(new ProductReviewMap());
            modelBuilder.Configurations.Add(new ProductSubcategoryMap());
            modelBuilder.Configurations.Add(new ScrapReasonMap());
            modelBuilder.Configurations.Add(new TransactionHistoryMap());
            modelBuilder.Configurations.Add(new TransactionHistoryArchiveMap());
            modelBuilder.Configurations.Add(new UnitMeasureMap());
            modelBuilder.Configurations.Add(new WorkOrderMap());
            modelBuilder.Configurations.Add(new WorkOrderRoutingMap());
            modelBuilder.Configurations.Add(new ProductVendorMap());
            modelBuilder.Configurations.Add(new PurchaseOrderDetailMap());
            modelBuilder.Configurations.Add(new PurchaseOrderHeaderMap());
            modelBuilder.Configurations.Add(new ShipMethodMap());
            modelBuilder.Configurations.Add(new VendorMap());
            modelBuilder.Configurations.Add(new CountryRegionCurrencyMap());
            modelBuilder.Configurations.Add(new CreditCardMap());
            modelBuilder.Configurations.Add(new CurrencyMap());
            modelBuilder.Configurations.Add(new CurrencyRateMap());
            modelBuilder.Configurations.Add(new CustomerMap());
            modelBuilder.Configurations.Add(new PersonCreditCardMap());
            modelBuilder.Configurations.Add(new SalesOrderDetailMap());
            modelBuilder.Configurations.Add(new SalesOrderHeaderMap());
            modelBuilder.Configurations.Add(new SalesOrderHeaderSalesReasonMap());
            modelBuilder.Configurations.Add(new SalesPersonMap());
            modelBuilder.Configurations.Add(new SalesPersonQuotaHistoryMap());
            modelBuilder.Configurations.Add(new SalesReasonMap());
            modelBuilder.Configurations.Add(new SalesTaxRateMap());
            modelBuilder.Configurations.Add(new SalesTerritoryMap());
            modelBuilder.Configurations.Add(new SalesTerritoryHistoryMap());
            modelBuilder.Configurations.Add(new ShoppingCartItemMap());
            modelBuilder.Configurations.Add(new SpecialOfferMap());
            modelBuilder.Configurations.Add(new SpecialOfferProductMap());
            modelBuilder.Configurations.Add(new StoreMap());
            modelBuilder.Configurations.Add(new vEmployeeMap());
            modelBuilder.Configurations.Add(new vEmployeeDepartmentMap());
            modelBuilder.Configurations.Add(new vEmployeeDepartmentHistoryMap());
            modelBuilder.Configurations.Add(new vJobCandidateMap());
            modelBuilder.Configurations.Add(new vJobCandidateEducationMap());
            modelBuilder.Configurations.Add(new vJobCandidateEmploymentMap());
            modelBuilder.Configurations.Add(new vAdditionalContactInfoMap());
            modelBuilder.Configurations.Add(new vStateProvinceCountryRegionMap());
            modelBuilder.Configurations.Add(new vProductAndDescriptionMap());
            modelBuilder.Configurations.Add(new vProductModelCatalogDescriptionMap());
            modelBuilder.Configurations.Add(new vProductModelInstructionMap());
            modelBuilder.Configurations.Add(new vVendorWithAddressMap());
            modelBuilder.Configurations.Add(new vVendorWithContactMap());
            modelBuilder.Configurations.Add(new vIndividualCustomerMap());
            modelBuilder.Configurations.Add(new vPersonDemographicMap());
            modelBuilder.Configurations.Add(new vSalesPersonMap());
            modelBuilder.Configurations.Add(new vSalesPersonSalesByFiscalYearMap());
            modelBuilder.Configurations.Add(new vStoreWithAddressMap());
            modelBuilder.Configurations.Add(new vStoreWithContactMap());
            modelBuilder.Configurations.Add(new vStoreWithDemographicMap());
        }
    }
}

 

在项目中我们还可以看到Entity Framework Power Tools自动创建了一个Models文件夹，这里除了“AdventureWorksContext”类还有所有的数据类。在Models文件夹下还有一个“Mapping”文件夹，这里放了数据类与数据库的映射配置类，可以看出Entity Framework Power Tools通过fluent API的方式进行映射细节配置（目前Entity Framework Power Tools还不支持Data Annotations方式），关于配置类的具体细节我们这里暂不进行详细介绍。

下面我们进行数据查询：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using EFPowerTools.Models;

namespace EFPowerTools
{
    class Program
    {
        static void Main(string[] args)
        {
            using (var db = new AdventureWorksContext())
            {
                var persons = db.People.Where(p => p.LastName == "Stevens").OrderBy(p=>p.FirstName);
                foreach(var p in persons)
                {
                    Console.WriteLine("FirstName:{0},LastName:{1}", p.FirstName, p.LastName);
                }
            }
        }
    }
}

查询结果：

自定义模板

事实上Entity Framework Power Tools的功能还远不止这些，例如我们上面谈到Entity Framework Power Tools使用fluent API进行映射配置，而通常情况下开发人员更喜欢使用Data Annotations方式进行映射约定，那么此时你就可以选择配置自己的模板。

在项目上右键选择Entity Frmaework->Customize Reverse Engineer Templates，此时会看到项目中添加了一个“CodeTemplates”文件夹，里面存放了Entity Framework Power Tools用于生产相关类文件的T4模板（对于不了解T4模板引擎的朋友可以点击这里Lowering the Barriers to Code Generation with T4），如果此时再使用Entity Framework Power Tools进行Code First反向工程操作将使用当前这个文件夹中的模板进行生成。接下来看一下如何进行模板自定义。

首先让我们打开Mapping.tt文件，这个文件主要用户生成配置类，在Entity Framework Power Tools默认生成的代码中通过fluent API进行表名和数据类名以及属性名同列名的对应配置，例如下面的代码：

下面让我们修改一下Mapping.tt文件，去掉上面的约束，而改用Data Annotations方式进行约定。首先去掉下图中选择的代码，此时生成的映射类中就不再出现上图中选择的代码部分：

然后我们需要修改Entity.tt模板，将数据库中的表和列的映射声明到数据类上。先让我们将数据类和表做对应，这需要在数据类上添加“Table”声明，标记出表名和架构名（EF默认会使用dbo架构），在如图位置添加如下代码：

<# 
        var tableName = (string)efHost.TableSet.MetadataProperties["Table"].Value ?? efHost.TableSet.Name; 
        var conventionTableName = System.Data.Entity.Design.PluralizationServices.PluralizationService 
                .CreateService(new CultureInfo("en")) 
                .Pluralize(efHost.EntityType.Name);

        var schemaName = (string)efHost.TableSet.MetadataProperties["Schema"].Value; 
        schemaName = string.IsNullOrWhiteSpace(schemaName) 
                ? "dbo" 
                : schemaName;

        if(schemaName != "dbo" || conventionTableName != tableName) 
        { 
#> 
    [Table("<#= tableName #>", Schema="<#= schemaName #>")] 
<# 
        }

#> 

这段代码主要处理逻辑是：当架构不是“dbo”或者表名的复数形式同表名不同时添加“Table”标记声明。之所以添加判断是因为EF的默认使用“dbo”架构并且EF在操作表的时候默认将数据类的复数形式作为表名。

接下来添加列标记声明，在如图位置添加如下代码即可：

      var columnName = efHost.PropertyToColumnMappings[property].Name; 
                if(code.Escape(property) != columnName) 
                { 
#> 
        [Column("<#= columnName #>")] 
<# 
                } 

这里只是简单的对列名和编码后的列名进行比较，不同则添加列标记，否则不添加（EF默认认为数据类属性名和表的列名相同）。

由于刚才添加的标记属性类在“System.ComponentModel.DataAnnotations.Schema” 命名空间下，因此最后还需要在模板头部添加该命名空间：

 

<# 
       if (efHost.EntityFrameworkVersion >= new Version(4, 4)) 
        { 
#> 
using System.ComponentModel.DataAnnotations.Schema; 
<# 
        } 
        else 
        { 
#> 
using System.ComponentModel.DataAnnotations; 
<# 
        } 
#>

由于之前的EF版本中“Table”和“Column”类不在“System.ComponentModel.DataAnnotations.Schema”命名空间而是在 “System.ComponentModel.DataAnnotations”命名空间中，因此这里我们还需要添加一个判断。

今天的内容先到此为止，关于如何使用fluent API及Data Annotations定义配置类来进行更多的映射控制请关注后面的文章。