What’s Good About Microsoft’s
.NET, C#, and ASP.NET?
Andy Gravell, May 2009
Introduction
• No system or platform is perfect, but
Microsoft .NET has some impressive features
– for use in our teaching and research
– for commercial software development
• The observations in this talk are drawn from
– personal experience
– comments from colleagues and students
– articles and white papers on the web
Disclosure
• Studied Mathematics, then Computer Science
• Worked as a programmer for seven years
– mostly at IBM’s Hursley lab
• Persuaded ECS to teach Theory of Computing
– but my current classes are in the area of ebusiness and web development
• As a member of DSSE, my research area was
Formal Methods
– but am more interested in Agile Methods now
The Evil Empire?
• When I was a student, IBM were considered
the evil empire
• Now Microsoft have been found guilty of anticompetitive behaviour, some colleagues are
reluctant to consider any of their software
• In fact, both IBM and Microsoft have been
successful in developing a number of popular
and useful technologies
– technology transfer & commercialisation
Contributions From Industry
IBM
• Computer architecture
• Operating systems
– OS/360, virtual machines
Microsoft
• Web services (with IBM)
• “Visual” programming
– visual basic, visual studio
• High level languages
• Programming languages
– Fortran (and PL/I)
– powershell, C#, F#, ...
• Relational databases
• Formal methods
– VDM, Z
• Open source (eg Linux)
• ODBC
• Software analysis tools
– security/crash/driver
– spec#
Why .NET?
• At the end of the 1990s, a faction in Microsoft
argued in favour of focussing on an Internet O/S
instead of Windows*
– M/S has continued to develop Windows, of course
– but also introduced .NET version 1 in 2002
• Possibly a consequence of Sun’s 1997 lawsuit
alleging Microsoft’s extended and incompatible
version of Java had breached their contract
*Breaking Windows, David Banks, Free Press 2001
What is .NET?
• Like Java, a multi-target platform
– .NET programs can run on desktop and mobile
Windows machines, and in the browser
– also on Linux/BSD/ OS X thanks to the mono project
• Unlike Java, there are ISO standards* for
– Common language infrastructure (run-time)
– C# programming language
• Unlike Java, .NET supports multiple languages
– C#, VB, C++, Ada, Cobol, F#, JScript, Python, Ruby, ...
*ISO/IEC 23270 and 23271
.NET is Popular in Industry
• The technical skills most cited in job adverts* are:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
SQL
13335 total ads
.NET
12683
SQL Server
11327
Windows
11075
C#
10053
Java
8220
Oracle 7446
ASP.NET 6981
UNIX
6527
XML
6402
*IT Jobs Watch UK
£40K average salary
£40K
£39K
£37K
£42K
£46K
£47K
£37K
£46K
£39K
What is ASP.NET?
• A framework for web applications
– framework = library + skeleton main program
• Typically used together with Visual Studio
– or Visual Web Developer Express Edition (free)
• Without these, web development is difficult:
– multi-skilled (text & graphical content, code)
– multi-language
• XHTML, CSS, JavaScript, OOPL, XML, SQL
– increasing demands on user experience
Web Controls
• ASP.NET web pages (aka web forms) are made
up of a number of ASP.NET web controls
– around 100 controls are provided, grouped into
– standard, data, validation, navigation, login, AJAX
• Can drag and drop these from the toolbox, or
code them via web form markup or OO code
• Each control has properties which allow you to
configure its appearance and behaviour
• You can also code your own, or buy extras
ASP.NET Page Life Cycle
• When a page/form is first loaded its markup is
parsed and an object created for each control or
standard HTML element
• Each object is initialised and its initial properties are
set according to the web form markup
• Events are called based on the page state and any
user interaction with the page via their browser
• The list/tree of controls is walked and each in turn is
asked to render itself (output HTML for the browser)
The Three Styles
• “Visual”
– drag and drop GUI/Web UI builder
– setting properties via forms and check boxes
• “Declarative”
– entering definitions of controls and properties
– using an XML based markup language
• “Programmatic”
– plain old fashioned (but OO) code
– allows for more dynamic interactions
Benefits of This Approach
• This event-driven style of development is very
similar to modern Windows programming
• Rich database-driven web applications can be
created using the (code-free) “visual” style
– complex logic can still be coded when needed
– and the different styles can be mixed
• Despite the multiple layers of translation,
ASP.NET web applications run as fast as
Java(EE), and use less code [Petstore benchmark]
Recent Developments
• The slides so far describe facilities already present in
ASP.NET versions 1.0 and 2.0
• Recent enhancements include
–
–
–
–
–
Silverlight/Moonlight (Flash competitor)
LINQ (Hibernate competitor)
MVC (Struts competitor)
Dynamic Data (Ruby on Rails competitor)
Chart controls
• LINQ in particular uses new C# language features
(Some of the) New Language Features
• C# 2.0 introduced
– partial classes, iterators, nullable types
• C# 3.0 introduced
– object and collection initialisers
– anonymous types and type inference
– lambda expressions and expression trees
– partial and extension methods
• Visual Basic has introduced most of these and
also XML literals
LINQ
• LINQ stands for Language INtegrated Query
• Adds a query sublanguage to C# and VB.NET
• Familiar (SQL-like) syntax
– using the C# language extensions listed above
• You can teach yourself LINQ using LINQPad*
– and the Microsoft 101 LINQ samples
*Albahari and Albahari: http://www.linqpad.net/
Simple LINQ Examples
• To select integers from 3 to 5 and their
squares:
from x in (new int[] {1,2,3,4,5})
where (x > 2)
select (new {x, square = x*x})
• This is a sugared version of
(new int[] {1,2,3,4,5})
.Where(x => x > 2)
.Select(x => new {x, square = x*x})
LINQ to SQL Queries
• Once a database mapping has been defined, a
database query can be coded similarly
from p in Policies
where (p.PolicyID > 1) orderby p.Type
select (new {p.Premium, p.Type})
• A query such as this is stored as an expression tree,
and executed lazily when the data is required
• The LINQ code is translated into an optimised SQL
query at run-time
Running the Simple Queries
Running Database Queries
Benefits of In Language Queries
•
•
•
•
Compile time (and IDE) type checking
Syntax highlighting, autocompletion
Eliminates SQL injection attacks
Extensible
– can also query XML and .NET collection classes
– and one query can combine all these sources
– and you can code your own LINQ methods
Summary
• Teaching C# and ASP.NET is worthwhile
– interested advanced language features
– simplifies professional web development
– already successful in ELEC2018 and COMP6003
• If you wish to promote your research with a rich
interactive web site, consider ASP.NET
• The IT industry has selected ASP.NET
– rich, flexible and powerful web controls and class libraries
– less code  higher productivity, lower maintenance
– high performance