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Beginning VB 2008 Databases From Novice to Professional phần 5

Mặc dù chúng tôi không sử dụng nó trong cuốn sách này, nếu bạn sử dụng dòng lệnh VB NET trình biên dịch, bạn có thể sử dụng Mẹo các tùy chọn trình biên dịch sau đây bao gồm các tài liệu tham khảo của các hội đồng yêu cầu: / r: System.dll / r: System.Data.dll / r: System.Xml.dll. | Simpo PDF Merge and Split Unregistered Version - http www.simpopdf.com CHAPTER 9 GETTING TO KNOW ADO.NET 147 Tip Though we don t use it in this book if you use the command-line VB .NET compiler you can use the following compiler options to include the reference of the required assemblies r System.dll r System.Data.dll r System.Xml.dll. As you can see from the namespaces ADO.NET can work with older technologies such as OLE DB and ODBC. However the SQL Server data provider communicates directly with SQL Server without adding an OLE DB or ODBC layer so it s the most efficient form of connection. Likewise the Oracle data provider accesses Oracle directly. Note All major DBMS vendors support their own ADO.NET data providers. We ll stick to SQL Server in this book but the same kind of VB .NET code is written regardless of the provider. Understanding ADO.NET Architecture Figure 9-1 presents the most important architectural features of ADO.NET. We ll discuss them in far greater detail in later chapters. Figure 9-1. ADO.NET architecture Simpo PDF Merge and Split Unregistered Version - http www.simpopdf.com 148 CHAPTER 9 GETTING TO KNOW ADO.NET ADO.NET has two central components data providers and datasets. A data provider connects to a data source and supports data access and manipulation. You ll play with three different ones later in this chapter. A dataset supports disconnected independent caching of data in a relational fashion updating the data source as required. A dataset contains one or more data tables. A data table is a row-and-column representation that provides much the same logical view as a physical table in a database. For example you can store the data from the Northwind database s Employees table in an ADO.NET data table and manipulate the data as needed. You ll learn about datasets and data tables starting in Chapter 13. In Figure 9-1 notice the DataView class in the System.Data namespace . This isn t a data provider component. Data views are used .