A more powerful signaling construct is provided by the Monitor class, via the static methods Wait and Pulse and PulseAll. The principle is that you write the signaling logic yourself using custom flags and fields enclosed in lock statementsand then introduce Wait and Pulse commands to prevent spinning.
There are occasions however when we want to take care of these details ourselves, and in this tutorial we learn how to access the database connection- and command-level settings in the TableAdapter. Introduction Throughout the tutorial series we have used Typed DataSets to implement the Data Access Layer and business objects of our layered architecture.
As discussed in the first tutorialthe Typed DataSet s DataTables serve as repositories of data whereas the TableAdapters act as wrappers to communicate with the database to retrieve and modify the underlying data. The TableAdapters encapsulate the complexity involved in working with the database and saves us from having to write code to connect to the database, issue a command, or populate the results into a DataTable.
There are times, however, when we need to burrow into the depths of the TableAdapter and write code that works directly with the ADO. In the Wrapping Database Modifications within a Transaction tutorial, for example, we added methods to the TableAdapter for beginning, committing, and rolling back ADO.
These methods used an internal, manually-created SqlTransaction object that was assigned to the TableAdapter s SqlCommand objects.
In this tutorial we will examine how to access the database connection- and command-level settings in the TableAdapter. In particular, we will add functionality to the ProductsTableAdapter that enables access to the underlying connection string and command timeout settings.
NET Framework contains a plethora of classes designed specifically to work with data. These classes, found within the System. Data namespaceare referred to as the ADO. Some of the classes under the ADO. NET umbrella are tied to a particular data provider.
You can think of a data provider as a communication channel that allows information to flow between the ADO. NET classes and the underlying data store. There are generalized providers, like OleDb and ODBC, as well as providers that are specially designed for a particular database system.
When programmatically accessing data, the following pattern is commonly used: Establish a connection to the database. There are separate ADO. NET classes for performing each of these steps. To connect to a database using the SqlClient provider, for example, use the SqlConnection class.
NET code ourselves because the TableAdapters auto-generated code includes the functionality needed to connect to the database, issue commands, retrieve data, and populate that data into DataTables.
However, there may be times when we need to customize these low-level settings.
Over the next few steps we will examine how to tap into the ADO. NET objects used internally by the TableAdapters.
Examining with the Connection Property Each TableAdapter class has a Connection property that specifies database connection information. This property s data type and ConnectionString value are determined by the selections made in the TableAdapter Configuration wizard.
Recall that when we first add a TableAdapter to a Typed DataSet this wizard asks us for the database source see Figure 1. The drop-down list in this first step includes those databases specified in the configuration file as well as any other databases in the Server Explorer s Data Connections.
If the database we want to use does not exist in the drop-down list, a new database connection can be specified by clicking the New Connection button and providing the needed connection information. As noted in the Creating a Data Access Layer tutorial, we can view the auto-generated TableAdapter code by going to the Class View window, drilling down to the appropriate class, and then double-clicking the member name.
Double-click the Connection property to see its code. The Connection property can also be assigned to a SqlConnection object. Exposing Connection-Level Settings The connection information should remain encapsulated within the TableAdapter and not be accessible to other layers in the application architecture.
However, there may be scenarios when the TableAdapter s connection-level information needs to be accessible or customizable for a query, user, or ASP. Note A connection string is a string that specifies database connection information, such as the provider to use, the location of the database, authentication credentials, and other database-related settings.Mastering C# Database Programming [Jason Price] on grupobittia.com *FREE* shipping on qualifying offers.
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