EFCodeFirst 数据库连接

EFCodeFirst 数据库连接

EFCodeFirst

数据库连接

1.NuGet安装实体命令

1. PM> Install-Package EntityFramework 
   

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2.数据库连接字符串

自动添加得app.Config大体如下：

1. <?xml version="1.0" encoding="utf-8"?> 
   

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2. <configuration> 
   

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3. <configSections> 
   

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4. <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=4.4.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" /> 
   

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5. </configSections> 
   

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6. <entityFramework> 
   

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7. <defaultConnectionFactory type="System.Data.Entity.Infrastructure.SqlConnectionFactory, EntityFramework"> 
   

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8. <parameters> 
   

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9. <parameter value="Data Source=(local); Database=Portal; User ID=sa; Password=; MultipleActiveResultSets=True" /> 
   

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10. </parameters> 
    

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11. </defaultConnectionFactory> 
    

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12. </entityFramework> 
    

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13. </configuration> 
    

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设置DefaultConnectionFactory之后，使用Entity Framework连接数据库不需再在其他地方进行设置，Entity Framework也不需要指定数据库连接。

通过配置connectionStrings

1. <?xml version="1.0" encoding="utf-8"?> 
   

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2. <configuration> 
   

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3. <connectionStrings> 
   

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4. <add name="PortalContext" connectionString="Data Source=(local); Database=Portal; User ID=sa; Password=; MultipleActiveResultSets=True" 
   

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5. providerName="System.Data.SqlClient" /> 
   

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6. </connectionStrings> 
   

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7. </configuration> 
   

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3.DbContext连接数据库

1. using System; 
   

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2. using System.Collections.Generic; 
   

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3. using System.Linq; 
   

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4. using System.Text; 
   

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6. using System.Data.Entity; 
   

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8. namespace Portal 
   

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9. { 
   

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10. public class PortalContext : DbContext 
    

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11. { 
    

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12. static PortalContext() 
    

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13. { 
    

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14. Database.SetInitializer<PortalContext>(null); 
    

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15. //Database.SetInitializer(new CreateDatabaseIfNotExists<PortalContext>()); 
    

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16. //Database.SetInitializer(new DropCreateDatabaseAlways<PortalContext>()); 
    

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17. //Database.SetInitializer(new DropCreateDatabaseIfModelChanges<PortalContext>()); 
    

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18. } 
    

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20. public PortalContext() 
    

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21. : base("name=PortalContext") 
    

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22. { 
    

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23. } 
    

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25. protected override void OnModelCreating(DbModelBuilder modelBuilder) 
    

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26. { 
    

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27. } 
    

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28. } 
    

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29. } 
    

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静态构造函数中设置数据库的初始化方式，在构造函数中指定App.config的connectionString。

3种初始化方式

• CreateDatabaseIfNotExists。默认，数据库不存在创建数据库。
• DropCreateDatabaseWhenModelChanges。数据模型发生改变的时候，先删除，后创建。
• DropCreateDatabaseAlways。总是先删除后创建，无论模型是否变化。
• Database.SetInitializer<PortalContext>(null); 关闭初始化功能。

4.基本常用设置

• 禁用延迟加载(Lazy Loading)
• 禁用关系数据的级联删除
• 禁用默认表名复数形式

1. // 禁用延迟加载 DbContext类中设置 
   

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2. this.Configuration.LazyLoadingEnabled = false; 
   

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3. // 禁用一对多级联删除 OnModelCreating方法中设置 
   

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4. modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>(); 
   

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5. // 禁用多对多级联删除 OnModelCreating方法中设置 
   

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6. modelBuilder.Conventions.Remove<ManyToManyCascadeDeleteConvention>(); 
   

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7. // 禁用默认表名复数形式 OnModelCreating方法中设置 
   

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8. modelBuilder.Conventions.Remove<PluralizingTableNameConvention>(); 
   

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