Lưu ý khả năng của thuật sĩ để xây dựng một mô hình từ một cơ sở dữ liệu hiện tại có thể bị giới hạn bởi quyền bảo mật và hạn chế đối với cơ sở dữ liệu tài khoản của bạn. Hãy chắc chắn rằng bạn có đủ quyền để các bảng cơ sở dữ liệu và các yếu tố mà bạn sẽ mô hình ứng dụng của bạn. | 226 Microsoft 4 Step by Step Note The wizard s capability to build a model from an existing database can be limited by security rights and restrictions imposed on your database account. Make sure you have sufficient rights to the database tables and elements that you will model in your application. Similar to the Data Source Configuration Wizard demonstrated in Chapter 1 Introducing 4 the Entity Data Model Wizard guides you through the database selection and connection process which serves four main purposes To build the connection string for both the model and the target database. Built upon standard connection strings this wizard adds EF-specific metadata keyvalue pairs that help the Framework access the three XML-based modeling layers. metadata res res res provider provider connection string Data Source local SQLExpress Initial Catalog StepSample Integrated Security True Connect Timeout 30 User Instance True In this sample the expected SQL Server connection string comes after three resource references that identify the Conceptual Schema Definition Language CSDL Store Schema Definition Language SSDL and Mapping Specification Language MSL modeling documents. To build an application-side storage layer that parallels the database-side tables views and stored procedures specified in the wizard. This layer appears within your application using the SSDL schema language a layer that is only indirectly accessible through the model designer. To create a conceptual model of the imported storage items. At first this model will be nearly identical to the logical organization of the storage layer. You will have the opportunity to adjust this model to meet the needs of your application. This layer is created using the CSDL schema and is presented in the visual designer as a series of database modeling objects on a design surface. To link the storage and conceptual models with mappings using the .
