1. CSE 136 - Lecture 4 Part 1

2. What is DAL?

3. DAL Requirement
 Database independent
 DAL implementation should allow easy swap of
database servers (SQL Server to Oracle)
 Configurable
 DAL selection can be controlled by configuration file
 Example: connection string should be in web.config
file or app.config
 Persisting the Application Object Model
 Save the info in memory (object-oriented data) to
disk (relational data)
 Example: In windows app, department chair saves his
non-finalized version of course planning for next
quarter.

4. DAL responsibilities
In one transaction:
1. Add new course
2. Update pre-req
3. Delete old course

5. DAL responsibilities - Object Mapping

6. DAL - query service

7. DAL - Transaction Management
 Keep track of all significant changes to the
application's data that occur in a unit of work
 A unit of work is a logical (business)
transaction that groups a number of database
calls
 Atomic - one indivisible operation
 Consistency - no data corruption when failure
occurs
 Isolated - Other operation can not see the
modified data until completion
 Durability - successful or failed transaction
notification

8. DAL and other layers

9. C# try/catch - exceptions

10. C# try/catch example

11. C# try/catch in DAL

12. ADO.NET
 A data provider is a set of ADO.NET classes (libraries)
 Allows you to access a specific database
 Execute SQL commands
 Retrieve data
 A bridge between your application and database
 Classes that make up a data provider include:
 Connection
 Establish a connection to database
 Command
 Execute SQL commands and stored procedures
 DataReader
 fast, read-only, forward-only access from a query
 DataAdapter
 Fill a DataSet***
 More on DataSet next

13. ADO.NET - connection and command

14. ADO.NET - Adapter & DataSet

15. ADO.NET - DataSet

16. ADO.NET - summary

17. Create a unit test
Create the DALTest
(class library project)
first

18. Create unit test code
Test the “Insert”
Assert: to validate the values match
Testing the “Get”
Clean up

19. Unit test project – App.config

20. Unit test, assert error, and watch

21. Unit test break point & debug

22. Review question
 What are the DAL’s major responsibilities?
 Why would you need transactions in the DAL?
 Why do you need try catch in DAL?
 What .NET library will you be using for DAL?
 Difference between DataSet and DataAdapter?
 What is assert.equal() method used for?
 Why do you need to have sql connection string
in the app.config when running unit tests?

23. Demo of VS 2010 O/RM
 Student info & enrollment in stored procedure
 Students Enrollment in DAL
 OR/M between database and DAL
 Run unit test in DAL

24. Your assignment for next week
 Set up your solution to include the following
"Class Library" projects
 DataAccessLayer project
 BusinessLayer project
 BusinessObjects project
 Develop the Data Access Layer code (CRUD)
 Unit Tests for your DAL

25. Lab
 Due: Grade your DB setup

26. References
 .NET : Architecting Applications for the
Enterprise