Application Architecture Guide 2.0 BETA 1 - Willy .Net

If you are designing a small Web application or a service, and you want to take advantage of
the disconnected behavior they provide, consider using DataSets. If you are working with
content-based applications that have few or no business rules, consider using XML. If you
have complex business rules related to the business domain, or if you are designing a rich
client where the domain model can be initialized and held in memory, consider using
custom Domain Model objects. If your tables or views in the database represent the
business entities used by your application, consider using custom Table Module objects. If
the data you are consuming is already in XML format, or if you are working with read-only
document-based data, consider using custom XML objects.
Data Access
The following guidelines will help you to understand the fundamental factors when designing
the data layer for your application.
• How to design your data connectivity strategy
If the client and the server are located on the same machine, use shared memory. If you
must support communication over the Internet, over wide area networks, or are dealing
with slow network connections, use TCP/IP. If the underlying database is Microsoft SQL
Server, use Named Pipes. If you must expose data directly from your database without
being required to create an intermediate interface, use HTTP Endpoints. When working with
HTTP Endpoints, use Web services as the communication mechanism. If you need a .NET
Framework managed provider for the database, use ADO.NET.
• How to choose between dynamic SQL and stored procedures
In the past, a primary reason for using stored procedures was the improvement in
performance compared to dynamic SQL statements. However, with modern database
engines, performance is no longer a factor in choosing one over the other. One of the
primary reasons for choosing stored procedures has to do with the fact that a database is
one of the top assets for an organization. A stored procedure provides an abstraction layer
that can be used to restrict access to underlying objects and mitigate system wide changes
when objects in the database need to change. Stored procedures also provide enhanced
security by reducing exposure to SQL Injection attacks, and providing a security model that
is much easier to manage. Avoid mixing dynamic SQL within a stored procedure. Avoid
mixing business logic in your stored procedures and in dynamic SQL. When using dynamic
SQL, use parameters to help protect against SQL injection attacks, and batch statements to
maximize performance. Consider maintainability. For example, decide if it is easier to
update statements in a stored procedure or SQL statements in the compiled code.
• How to improve data access performance
Minimize processing on the server and at the client. Minimize the amount of data passed
over the network. Use database connection pooling to share connections across requests.
Keep transactions as short as possible to minimize lock durations and to improve
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