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<title>Design of EasyObjects.NET</title>
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<h1 class="dtH1">Design of the EasyObjects.NET</h1>
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<p>EasyObjects.NET includes the following features:</p>
<ul>
<li>A simple and efficient way of working with commonly used databases.
</li>
<li>Transparency when developing for multiple types of databases.</li>
<li>Mapping between logical database instance names and physical
connections.</li>
<li>Strongly-typed properties that match the database table or view
columns.</li>
<li>Support for advanced database features, including dynamic queries,
null value handling and transaction support.</li>
<li>Support for the Enterprise Library Configuration Tool.</li>
</ul>
<h2>Design Goals</h2>
<p>EasyObjects.NET was designed to achieve the following goals:</p>
<ul>
<li>To encapsulate the logic used to perform the most common data access
tasks.
</li>
<li>To relieve developers of the need to write duplicate code for common
data access tasks.
</li>
<li>To simplify and abstract custom query operations.
</li>
<li>To perform within 5 percent of ADO.NET's efficiency.
</li>
<li>To be syntactically compatible with
<a href="http://www.mygenerationsoftware.com/portal/dOOdads/Overview/tabid/63/Default.aspx">
MyGeneration's dOOdads architecture</a>.
</li>
<li>To ensure that all the application block's functions work
identically for different types of databases.
</li>
<li>To ensure that applications written for one type of database are, in
terms of data access, the same as applications written for another type
of database.
</li>
</ul>
<h2>Design Highlights</h2>
<p>The following illustration shows the interrelationship between the key
classes in the Data Access Application Block.</p>
<p class="fig">
<img alt="EasyObjects Class Diagram" src="EasyObjects.gif" border="0"></p>
<p class="label"><b>Figure 1:</b> <i>Design of the EasyObjects.NET</i></p>
<p>The abstract base class <b>EasyObject</b> defines the common interface
and provides much of the implementation for the data access methods. All of
the business object concrete classes inherit from the EasyObject class.
Because EasyObjects.NET is built on the Enterprise Library's Data Access
Application Block, it provides common functionality that
is implemented differently from database to database, as well as
functionality unique to that database system.</p>
<p>Query commands and syntax differ across database
systems. The abstract class <b>DynamicQuery</b> provides the base class
definition for database-specific classes that will implement the query
syntax
and parameter handling.</p>
<p>The <b>DynamicQueryFactory</b> class provides a static method, <b>
DynamicQuery</b>, to encapsulate the logic that creates the appropriate
database provider object. By using the factory to create the correct object, the client code is not bound to a specific database type.
Developers can also create their own custom providers, including replacing
the included providers.</p>
<p>The <b>DynamicQueryFactory</b> class uses the Configuration Application Block
to retrieve the required configuration information, including the fully
qualified type name and the assembly name of the specific <b>DynamicQuery</b>-derived
class to be created.</p>
<p>EasyObjects.NET supports automatic transaction handling. The <b>
TransactionManager</b>
class allows all EasyObjects on the same connection to participate in the
same transaction, <i>without the need to pass a transaction object around</i>. </p>
<p>The <b>SchemaItem</b> class contains meta-data from the database table,
including field lengths and database type. The <b>Schema</b> class is a
collection of SchemaItems.</p>
<p>The <b>WhereParameter</b> class is used for constructing
database-independent dynamic queries.</p>
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