High Level Overview of CS 3500 C#

Programming techniques

Software architecture

Software development tools

Personal software practice

Other topics

CS 3500 L20 - 2

C# Programs organized into namespaces Namespaces contain classes and interfaces Programs can be assembled into executables Programs can be assembled into DLLs Implementing classes, methods, properties Inheritance and interfaces IEnumerable<T> and IEnumerator<T> Delegates Events LINQ

Programming Techniques (1) Iteration abstraction– Iterative access to members of a collection– Cursors (similar to Java iterators)– IEnumerator interface– C# iterators (via yield return)– Visitor OO design pattern

Delegates– Passing methods as parameters– Customizing sorting and searching algorithms– Registering callbacks – Launching threads

Programming Techniques (2) Events– Asynchronous behavior that triggers callbacks – Implementing GUI interfaces– Using asynchronous sockets

Threading– An approach to concurrency– Synchronization with locks– Avoiding deadlocks – Critical sections– GUI event thread– Asynchronous sockets

Programming Techniques (3)

Socket Programming– For communication over a network – Servers accept, clients connect– Synchronous blocking sockets– Asynchronous non-blocking sockets

SQL Programming

– Incorporating databases into programs– Designing database schema– Imposing keys and constraints– Queries (selection, projection, join)– Insert, delete, update

Programming Techniques (4)

Object-Oriented Design Patterns

– Solutions to commonly-encountered problems

– Singleton pattern

– Factory pattern

– Adapter pattern

– Decorator pattern

– Visitor pattern

– There are many more!

Software Architecture (1) Object-oriented architecture– Organizing programs around classes– Information hiding– Exploiting polymorphism via inheritance and

intefaces

Client/server architecture– Network-based approach– Server program that accepts connections from

remote clients– Client programs that requests connections to

remote servers– Typically involves sockets and threads

architecture

Software Architecture (2) Event-driven architecture

–Programs organized around asynchronous events that are handled via calls to registered callbacks

– Typically involves threads

GUI architecture

– Users interact with programs via GUI components

– Relies heavily on events and callbacks

Software Architecture (3) MVC architecture– Model: The “smarts” or “business logic”– View: The user interface– Controller: Mediates between model and

view

Database-oriented architecture– Program makes use of database, typically

via remote server– Program can benefit from ACID

properties of database (atomicity, consistency, isolation, durability)

CS 3500 L20 - 10

Software Development Tools

Program development (VS) GUI construction (VS) Version control (SVN) Debugging (from VS) Unit testing (from VS) Coded UI testing (from VS) Database management

CS 3500 L20 - 11

Software Engineering

Evolution from custom batch applications to networked, parallel, object-oriented systems

Software crisis is an age-old issue in computer science

Idealized vs. actual failure rates for software Software engineering as intersection of systems

engineering, computer science, management, and psychology

Software lifecycle: analysis, design, development, testing, maintenance

Need process to identify and correct problems early

CS 3500 L20 - 12

Version Control

Keep track of the evolution of programs, documentation, tests, etc. as they evolve

When developing alone, solves the multiple machine problem, allows recovery from mistakes

When working with others, supports coordination of efforts and resolution of conflicts

Software Testing

Goal of testing is to affirm quality Testing: process of executing a program with the

intent of finding an error (up to 40% of SE effort) Testing cannot show the absence of defects Testing models:

– Black box testing

– White box testing

– Unit testing

– Test-first approach

Testing in practice: unit tests Testing in practice: coded UI tests

Debugging

A bug is a defect (a mistake) and you put it there! Debugging is difficult, takes an unpredictable

amount of time, and most people aren’t systematic Experienced debuggers are roughly 20 times better

at finding defects Process: Stabilize the error, locate the error, fix the

error, test the fix, look for similar errors, reflect Locating errors: Narrow the region of suspicious

code, come up with hypotheses, and devise tests to confirm/refute them

Improving program performance

Making simple source modifications to improve efficiency isn’t worth it because compilers are so good

However, no compiler can compensate for your choice of an inefficient algorithm or data structure

Before attempting to improve program performance, obtain timing measurements so you’ll know what to target and whether you succeeded

Before attempting to improve program performance, develop regression tests to assess correctness

Pareto principle: 80% of the result with 20% of the effort Pay attention to virtual memory and cache effects

Pair programming

Two programmers working side-by-side at one computer

Can produce higher-quality code with less effort than two programmers working individually

Works because of pair-pressure, pair-think, and pair-relaying, pair-reviews, and pair-learning

UML

Graphical notation for describing aspects of software at a higher level of abstraction

Class diagrams are used to describe salient parts of class hierarchies

Even though graphical, there is a syntax and semantics

Intellectual property

Copyright: Protects creative expression in many forms, including software– Fair use doctrine provides exception to copyright

– Digital media allow perfect copies and easy transmission, all with little expense

– Laws changing rapidly in digital age

– DMCA provides for notice and takedown and anticircumvention

Patent: Protects novel inventions – Expensive and time-consuming to obtain

– System has been abused, especially for software patents

Trademarks: Protects symbols used for branding Trade secrets: Alternative to patents

Ethics

Act consistently with the public interest Act in the best interest of employer and client,

consistent with the public interest Products should meet highest standards possible Maintain integrity in professional judgment Subscribe to ethical approach to management Advance integrity and reputation of profession Be fair to and supportive of colleagues Participate in lifelong learning