How Does ADO. NET Work? NET leverages. NET data providers to connect to a database, execute commands, and retrieve results. The ADO. NET object model exposes very flexible components, which in turn expose their own properties and methods, and recognize events. NET object model and the role of each object in establishing a connection to a database and manipulating its tables. Not quite. NET, you should try to use the managed. NET data providers whenever possible. This leads to performance degradation. NET providers, such as the System. NET data providers completely.
If you are using anything other than SQL Server 7 or , you might not have another choice. Although you will experience performance gains with the SQL Server. NET Framework for performance concerns. NET providers. NET data provider, which exposes only a subset of this full functionality. Another caveat to the SQL Server. NET data provider is that it is tightly coupled to its data source.
Although this enhances performance, it is somewhat limiting in terms of portability to other data sources. If you are so inclined, you can write your own. NET data providers for any data source by inheriting from the System. Data namespace. At this time, the. NET data provider for data access within the.
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Microsoft expects the support for. NET data providers and the number of. NET data providers to increase significantly. In fact, the ODBC. A major design goal of ADO. NET is to synergize the native and managed interfaces, advancing both models in tandem. NET objects within the System.
When you create a new VB. NET project, a reference to the System. Data namespace will be automatically added for you, as you can see in Figure 6. Figure 6. NET, reference the System.
To comfortably use the ADO. NET objects in an application, you should use the Imports statement. By doing so, you can declare ADO. NET variables without having to fully qualify them. You could type the following Imports statement at the top of your solution: Imports System. NET objects without having to fully qualify the class names.
NET code for you. NET objects. Nevertheless, before you use these tools to build production systems, you should understand how ADO.
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NET works programmatically. By understanding how to program against the ADO. NET object model, you will have more power and flexibility with your data access code. NET as being composed of two major parts:. NET data providers and data storage. Respectively, these fall under the connected and disconnected models for data access and presentation. NET data providers, or managed providers, interact natively with the database.
NET data provider classes are optimized for fast, read-only, and forward-only retrieval of data. The managed providers talk to the database by using a fast data stream similar to a file stream. This is the quickest way to pull read-only data off the wire, because you minimize buffering and memory overhead. If you need to work with connections, transactions, or locks, you would use the managed providers, not the DataSet. The DataSet is completely disconnected from the database and has no knowledge of transactions, locks, or anything else that interacts with the database.
Five core objects form the foundation of the ADO. NET object model, as you see listed in Table 6. Microsoft moves as much of the provider model as possible into the managed space. NET data provider, whereas the DataSet is part of the disconnected data storage mechanism. Table 6. NET Core Components Object Description Connection Creates a connection to your data source Command Provides access to commands to execute against your data source DataReader Provides a read-only, forward-only stream containing your data DataSet Provides an in-memory representation of your data source s DataAdapter Serves as an ambassador between your DataSet and data source, proving the mapping instructions between the two Figure 6.
NET object model. NET completely factors out the data source from the actual data. Each object exposes a large number of properties and methods, which are discussed in this and following chapters.
NET Framework. NET contains a collection-centric object model, which makes programming easy if you already know how to work with collections. Four core objects belong to. The Connection object is the simplest one, because its role is to establish a connection to the database. The Command object exposes a Parameters collection, which contains information about the parameters of the command to be executed.
The DataReader object provides fast access to read-only, forward-only data, which is reminiscent of a read-only, forward-only ADO RecordSet. The DataAdapter object contains Command objects that enable you to map specific actions to your data source. The DataAdapter is a mechanism for bridging the managed providers with the disconnected DataSets. NET managed provider architecture. The DataTables collection can be used in conjunction with the DataRelation collection to create relational data structures. First, you will learn about the connected layer by using the.
NET data provider objects and touching briefly on the DataSet object. Next, you will explore the disconnected layer and examine the DataSet object in detail. Note Although there are two different namespaces, one for OleDb and the other for the SqlClient, they are quite similar in terms of their classes and syntax. As we explain the object model, we use generic terms, such as Connection, rather than SqlConnection.
NET in detail. NET Programming. The Connection object establishes a connection to a database, which is then used to execute commands against the database or retrieve a DataReader.source url
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The ConnectionString property is the most important property of the Connection object. This string uses name-value pairs to specify the database you want to connect to. To establish a connection through a Connection object, call its Open method. When you no longer need the connection, call the Close method to close it. To find out whether a Connection object is open, use its State property.
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