Inherit from the Business Class Library Class 继承自Business类(EF)

In this lesson, you will learn how to implement business classes for your application using the Business Class Library. This library contains the most typical ready-to-use business classes. You will implement a custom Contact class by deriving from the Person class available in this library, and implement several additional properties. You will also learn the basics of automatic user interface construction based on data.

在本课中，您将学习如何使用 Business 类库为应用程序实现业务类。此库包含最典型的即用型业务类。您将通过从此库中可用的 Person 类派生来实现自定义联系人类，并实现多个附加属性。您还将学习基于数据的自动用户界面构造的基础知识。

• Typically, business classes should be implemented in a platform-independent module project, so that the same objects will be available in both WinForms and ASP.NET applications. To add a new class, right-click the Business Objects folder in the MySolution.Module project, and choose Add | Class... to invoke the Add New Item dialog. In this dialog, specify "Contact" as the new item's name and click Add. As a result, you will get an automatically generated code file with a single class declaration.

• 通常，业务类应在独立于平台的模块项目中实现，以便 WinForms 和ASP.NET应用程序中都提供相同的对象。要添加新类，请右键单击 MySolution.模块项目中的"业务对象"文件夹，然后选择"添加 |类。。。以调用"添加新项"对话框。在此对话框中，将"联系人"指定为新项目的名称，然后单击"添加"。因此，您将获得一个自动生成的代码文件，其中只有一个类声明。

  

• Replace the automatically generated class declaration with the following code.

• 将自动生成的类声明替换为以下代码。

  using System;
  using DevExpress.ExpressApp.DC;
  using DevExpress.Persistent.Base;
  using DevExpress.Persistent.BaseImpl.EF;
   
  namespace MySolution.Module.BusinessObjects {
      [DefaultClassOptions]
      public class Contact : Person {
          public Contact() { }
   
          public string WebPageAddress { get; set; }
          public string NickName { get; set; }
          public string SpouseName { get; set; }
          public TitleOfCourtesy TitleOfCourtesy { get; set; }
          public DateTime? Anniversary { get; set; }
          [FieldSize()]
          public String Notes { get; set; }
      }
      public enum TitleOfCourtesy { Dr, Miss, Mr, Mrs, Ms };
  }

  As you can see, the Contact class ancestor is Person from the Business Class Library and several custom properties are implemented.

• 如您所见，联系人类祖先是来自 Business 类库中的人员，并且实现了多个自定义属性。

• Note the use of the DefaultClassOptionsAttribute attribute. In this tutorial, this attribute means that the following capabilities will be available for the Contact business class.

• 请注意使用默认类选项属性属性。在本教程中，此属性表示以下功能将可用于联系人业务类。

• The Contact item will be added to the main form's navigation control. When clicking this item, a List View will be displayed. This List View represents a list of objects of the Contact type.
• The Contact item will be added to the submenu of the New () button when objects of another type are displayed in the List View. Click this item to invoke a Contact detail form and create a new Contact object.
• The Contact objects will be provided as a data source to generate reports (see Create a Report in Visual Studio).
• 联系人项将添加到主窗体的导航控件中。单击此项目时，将显示列表视图。此列表视图表示联系人类型的对象的列表。
• 当另一种类型的对象显示在列表视图中时，联系人项将添加到"新建（new_dropdown_btn）"按钮的子菜单中。单击此项目可调用"联系人详细信息"窗体并创建新的"联系人"对象。
• 联系人对象将作为数据源提供以生成报告（请参阅在 Visual Studio 中创建报表）。

• To apply each of these options separately, use the NavigationItemAttribute, CreatableItemAttribute and VisibleInReportsAttribute attributes.

• 要单独应用每个选项，请使用导航项属性、可操作项属性和可见中报表属性属性。

• After the class declaration, add all new business objects to the solution's DbContex

• 类声明后，将所有新的业务对象添加到解决方案的 DbContext

• Since Contact is a descendant of Person, entities used in the Person class should also be registered. Edit the BusinessObjects\MySolutionDbContext.cs file as shown below.

由于"联系人"是 Person 的后代，因此还应注册 Person 类中使用的实体。编辑业务对象_MySolutionDbContext.cs 文件，如下所示。

using MySolution.Module.BusinessObjects;
 
namespace  MySolution.Module.BusinessObjects {
    public class MySolutionDbContext : DbContext {
        //...
        public DbSet<Contact> Contacts { get; set; }
        public DbSet<Party> Parties { get; set; }
        public DbSet<Address> Addresses { get; set; }
        public DbSet<Country> Countries { get; set; }
        public DbSet<State> States { get; set; }
        public DbSet<PhoneNumber> PhoneNumbers { get; set; }
        public DbSet<Task> AssignedTasks { get; set; }
    }
}

• At this step, the business model has already been declared, but if you have started the application with another version of DbContext, you will get the following error: "The model backing the 'MySolutionDbContext' context has changed since the database was created. Consider using Code First Migrations to update the database (http://go.microsoft.com/fwlink/?LinkId=238269)". To avoid this error, drop the database every time you change something in the business model (create a new class, add a new attribute to an existing class, rename a class or an attribute, etc.). To do it automatically during the debug, uncomment the following code in the MySolution.Module\Module.cs file.

• 在此步骤中，业务模型已声明，但如果已使用另一个版本的 DbContext 启动应用程序，则将出现以下错误："自创建数据库以来，支持"MySolutionDbContext"上下文的模型已更改。请考虑使用代码优先迁移来更新数据库 （http://go.microsoft.com/fwlink/?LinkId=238269）*。为了避免此错误，每次更改业务模型中的内容时都删除数据库（创建新类、向现有类添加新属性、重命名类或属性等）。要在调试期间自动执行此操作，请取消在 MySolution.module_module_模块.cs 文件中对以下代码进行注释。

  public sealed partial class MySolutionModule : ModuleBase {
      // Uncomment this code to delete and recreate the database each time the data model has changed.
      // Do not use this code in a production environment to avoid data loss.
      #if DEBUG
      static MySolutionModule() {
          Database.SetInitializer(new DropCreateDatabaseIfModelChanges<MySolutionDbContext>());
      }
      #endif
      //...
  }

• Run the WinForms or ASP.NET application. You will see how the user interface is automatically generated using the specified data structures. A navigation control allows you to display the Contact list. You can customize this collection using the corresponding editors. If you click the New button or double-click an existing record, the application will show a detail form (Detail View) filled with editors for each data field.

• 运行 WinForms 或ASP.NET应用程序。您将看到如何使用指定的数据结构自动生成用户界面。导航控件允许您显示联系人列表。您可以使用相应的编辑器自定义此集合。如果单击"新建"按钮或双击现有记录，应用程序将显示一个详细信息表单（详细信息视图），其中填充了每个数据字段的编辑器。

• The following image demonstrates the Detail and List Views in the WinForms application.

• 下图演示了 WinForms 应用程序中的详细信息视图和列表视图。

  

  Notice that many elements have been generated in an intuitive manner in very little time. The proper editors are created for data fields, and appropriate editors are used in the grid controls to display data. Note that a combo box editor has been created for Title Of Courtesy (an enumerator). Also note that captions have automatically been transformed from camel-case to space-separated strings, form titles are automatically updated, etc.

• 请注意，许多元素是在非常少的时间内以直观的方式生成的。为数据字段创建适当的编辑器，并在网格控件中使用适当的编辑器来显示数据。请注意，已为礼貌标题（枚举器）创建了组合框编辑器。另请注意，标题已自动从骆驼大小写转换为空格分隔的字符串，表单标题会自动更新，等等。

• You can use the grid features to show, hide and rearrange columns, and apply grouping, filtering and sorting to a List View at runtime. In the WinForms application, you can customize the editor layout on the detail form as you like at runtime. For this purpose, right-click an empty space and select Customize Layout. You can now move editors to the required positions. To learn how to customize the editor layout at design time, refer to the Customize the View Items Layout topic. Additionally, you can refer to the View Items Layout Customization and List View Column Generation topics to see how the default Detail View layout and default List View column set are generated.

• 您可以使用网格要素来显示、隐藏和重新排列列，并在运行时对列表视图应用分组、筛选和排序。在 WinForms 应用程序中，您可以在运行时根据需要自定义详细信息窗体上的编辑器布局。为此，右键单击空白区域并选择"自定义布局"。您现在可以将编辑器移动到所需的位置。要了解如何在设计时自定义编辑器布局，请参阅自定义视图项布局主题。此外，还可以参考"查看项目布局自定义"和"列表视图列生成"主题，以查看如何生成默认"详细信息视图"布局和默认列表视图列集。

You can see the code demonstrated here in the MySolution.Module | Data | Contact.cs (Contact.vb) file of the EF Demo (Code First) installed with XAF. By default, the EF Demo (Code First) application is installed in %PUBLIC%\Documents\DevExpress Demos 19.2\Components\eXpressApp Framework\EFDemoCodeFirst.

您可以在 MySolution.模块 |数据 |Contact.cs（Contact.vb）文件与XAF一起安装的EF演示（代码优先）文件。默认情况下，EF 演示（代码优先）应用程序安装在 %PUBLIC%\Documents\DevExpress Demos 19.2\Components\eXpressApp Framework\EFDemoCodeFirst.