2. Chris Menegay Sr. Consultant TECHSYS Business Solutions
Data Access Patterns
Chris Menegay
Sr. Consultant
TECHSYS Business Solutions

3. Agenda Data Access Methodology Techniques for Data Access Summary
Data Access Layer
Techniques for Data Access
ADO.NET
Datasets
Datareaders
Microsoft Data Access Application Blocks
SQLXML
Summary

4. Data Most applications deal with data that is persisted in some manner
RDBMS
Flat file
Mainframe
XML
Need a consistent way to write code to take application data and persist it.

5. Selecting a Solution There is more than one ‘right way’
You are part of the answer…
…your skills …your background
…your familiarity
What are you doing with the data?
Does it contain business logic?
What tools are you using with it?
What is the destination of the data?
Are you exchanging it with other partners?
What type of project are you working on?
Self-contained app versus enterprise framework

6. Layered Architecture Pattern
Users
Operational Management
Security
Communication
UI Components
UI Process Components
Service Interfaces
Business Workflows
Business Components
Business Entities
Data Access Components
Service Agents
Data
Sources
Services

7. Data Access Layer Contains all data access code.
Contains only data access code.
Does not contain business code.
Does not contain UI code.
Tip: Use IDBConnection, IDBCommand, etc.

8. Q: Why am I doing this? Consistency and Maintenance
It scales – works for small applications as well as large ones
Never have to wonder ‘where is all the code that accesses the customer table?’
Tip: you can code generate a lot of this

9. Data Access Layer

10. ADO.NET Data Access Support
Data is relational is objects is XML is Data
Technology Strengths Use if…
DataSet and DataReader
in ADO.NET
Relational (tabular) model
Highest performance
Explicit control
Fully exposes database functionality
You are comfortable with the relational model
You require maximum control/performance/functionality
You are using UI bound controls
Interoperability. Format for the Web – B2B, A2A
Sparse (semi-structured) data
XML Services e.g. XQuery, XSD
Relational mapping via metadata
Decoupled from database schema
You need to query data from XML data sources e.g. XML Web Services
You use vertical industry XML schemas for content publishing e.g. XBRL, RIXML, FinXML
You need to load XML documents into database tables
You are using UI bound controls for XML
SQLXML in
ADO.NET

11. DataSets And Datareaders
Use Datasets for:
Holding data in memory – great for winforms applications with databinding.
Allow sorting and filtering at the client
Combine results from multiple stores
Use Datareaders for:
Read once data
Speed

12. Data Access Helpers

13. Why a helper block? Consistent mechanism for accessing data
Simplifies code

14. Microsoft Data Access Application Block

15. DataSets And Data Providers
Overview
Architecture
Scenarios
Demo

16. .NET Data Providers: Overview
Goal: Integrate manipulation of relational data with the .NET Framework
Accessing a Relational Store (.NET Data Providers)
Connecting, Executing Commands, Retrieving Results
Explicit Architecture
Provided a defined interface:
IDBConnection
IDBCommand, etc
Predictable behavior, semantics
Optimized performance

17. DataSet And Data Providers: Architecture
DataAdapter
.NET Data Provider
DataReader
Command
Connection

18. Data Providers & Helper Blocks

19. SQLXML
Overview
Architecture
Scenarios
Demo

20. SQLXML: Overview
Growing number of applications unifying under XML based interfaces
Loose coupling
Coping with decentralized data
Managing sparse (semi-structured) data
SQLXML supports XML over SQLServer
XML programming model for queries and updates
XQuery(Whidbey) - Full fledged XML query language
XML Views
Mapping technology to expose logical XML views of SQL Server relational tables
XML Views provide XQuery support over SQL Server.

21. ADO.NET With SQLXML

22. SQLXML: Scenarios Represent data as XML Source and sink for XML
Content management systems, B2B scenarios
Queries and updates against XML Views
Loading large XML data sets
Bulk load data into existing relational table structure
E.g. Catalog information
Transfer data as XML between databases
Agree on transfer format
Apply mappings at either end

23. SQLXML

24. Summary It’s all about DATA…
Plan how you want to access/maintaing your data
Structure your code!
Understand the strengths of each technology
DataSet and Datareader
Relational Model
Ultimate Performance, Control
SQLXML
XML Model
Interoperable, self-describing format
Pick the technology appropriate to your scenario
How results will be used
Tools to be applied
Your knowledge/comfort level

25. Call To Action
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