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 e-

business 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 anti-competitive 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

• High level languages– Fortran (and PL/I)

• Relational databases• Formal methods

– VDM, Z

• Open source (eg Linux)

Microsoft• Web services (with IBM)• “Visual” programming

– visual basic, visual studio

• Programming languages– powershell, C#, F#, ...

• 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. SQL 13335 total ads £40K average salary2. .NET 12683 £40K3. SQL Server 11327 £39K4. Windows 11075 £37K5. C# 10053 £42K6. Java 8220 £46K7. Oracle 7446 £47K8. ASP.NET 6981 £37K9. UNIX 6527 £46K10. XML 6402 £39K

*IT Jobs Watch UK

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 Policieswhere (p.PolicyID > 1) orderby p.Typeselect (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