Creating Objects Using the Static Factory Methods

The Enterprise Library application blocks include static factory methods that you can use to create application block objects. These static methods implement the Factory pattern to instantiate providers. This means that if your applications use these static factory methods, they do not require any information about the specific implementation of the provider being created.

The Enterprise Library Core provides the support for creating objects that require configuration information. Figure 1 illustrates how the Enterprise Library Core builds these objects.

Figure 1
Application block factories use of the Enterprise Library Core

Note:
The SqlConfigurationSource shown in Figure 1 is implemented in the QuickStart named SqlConfiguration that demonstrates how you can store configuration information in a database.

The following code shows how an application that uses the Data Access Application Block DatabaseFactory class can create a Database object.

The Database class is an abstract class and defines the common interface for the provider implementations. The static method CreateDatabase returns a specific provider implementation type object (for example, a SqlDatabase object.) The type of object returned is determined by application configuration information.

The static factory methods use configuration information from the default configuration source. You can use the Configuration Console to define the default configuration source for your application configuration. If you do not define a configuration source, the static factory methods will use the System Configuration Source. This means that your configuration information must be stored in your application configuration file (App.config or Web.config).

The Configuration Console stores information for the configuration sources in the application configuration file. The following XML shows a configuration section in the application configuration file that defines two configuration sources.

<enterpriseLibrary.ConfigurationSource selectedSource="systemSource">
  <sources>
    <add name="fileSource"
         type="Microsoft.Practices.EnterpriseLibrary.Common.Configuration.FileConfigurationSource,
              Microsoft.Practices.EnterpriseLibrary.Common"
         filePath="test.exe.config"/>
    <add name="systemSource" 
         type="Microsoft.Practices.EnterpriseLibrary.Common.Configuration.SystemConfigurationSource,
              Microsoft.Practices.EnterpriseLibrary.Common"/>
  </sources>
</enterpriseLibrary.ConfigurationSource>