Microsoft .NET Basics

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Microsoft .NET Basics

• Daragh Byrne EPCC

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Purpose

• Microsoft .NET Framework
• Microsoft Intermediate Language (MSIL)
• Common Language Runtime (CLR)
• Class Libraries
• Language Compilers
• Distributed and Web-based computing
• .NET Programming with C

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• Microsoft .NET Framework

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.NET Framework

• Microsoft .NET is a set of Microsoft software
  technologies for connecting information, people,
  systems and devices
• http//www.microsoft.com/net/basics/whatis.asp
• In real terms to the developer
• A new platform for building applications that run
  in stand-alone mode or over the Internet

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Evolution

• Next Generation of COM
• Component oriented software is a good thing
• Win32/C-style APIs are outdated
• COM was step in right direction, but painful to
  program with
• COM was restricted to VB, C
• Binary compatibility/portability an issue x86
  version of COM component needed to be compiled
  for e.g. PowerPC
• Memory management also a pain
• Common Object Runtime
• An execution environment for components written
  in any language
• Eventually became .NET with incorporation of Web
  Services
• Standardised API
• Web Services
• Interoperability is key in the connected world
• Require open standards for interoperability and
  leveraging legacy code

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Whats in the .NET Framework?
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Targeting .NET
Source Code (C, VB.NET)
MSIL

• Compiled to

Runs on
CLR
Compiled to
Native Code (x86 etc)
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Microsoft Intermediate Language (MSIL)

• A machine-independent assembly language
• Similar in nature to Java byte-code
• Target language for all .NET compilers
• JIT-compiled (Just-In-Time) by the CLR to native
  code
• Very efficient late compilation approach
• Collection of IL known as a managed Assembly
• Library or executable (JAR in Java-speak)
• Can examine with ILDasm
• Disassembler
• Comes with the framework
• Possible to implement interpreter/runtime on any
  platform
• Open standards

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MSIL Example

• Example method body
• // Code size 21 (0x15) .maxstack 2
• .locals init (0 string
  CS0000000300000000) IL_0000 ldarg.0
  IL_0001 ldfld string NDoc.Core.HtmlHelp_p
  rojectName IL_0006 ldstr ".hhk
  IL_000b call string mscorlibSystem.Strin
  gConcat(string,
• 
  string) IL_0010 stloc.0
  IL_0011 br.s IL_0013 IL_0013 ldloc.0
  IL_0014 ret
• Yuck!
• Thankfully we dont have to deal with this
• Thats what compilers are for!
• You could do it though!

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Common Language Runtime

• The environment in which all .NET applications
  run
• Somewhat like the Java Virtual Machine
• With explicit multi-language support
• With explicit version control at assembly level
• JIT-compiles to native code
• Deals in the abstract with types
• classes, structs, interfaces etc.
• Handles instances, interactions between instances
• Provides runtime services for Managed Code
• Type control, exception handling, garbage
  collection threading etc.
• Removes mundane/dangerous tasks from the
  programmer

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Running a .NET Application
.NET Executable (Stored as Windows Portable
Executable file)
mscoree.dll
Bind to runtime library
Execute MSIL entry point (verifies code, starts
compilation and execution)
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Types and Assemblies

• Fundamentally the CLR deals with instances of
  types
• Has a unified type system
• Everything descends from System.Object type
• Divided into value types or reference types
• Value types are primitives, structs, enums etc
  and live on the stack
• Derived from the System.ValueType type
• Reference types are instances of classes,
  interfaces, arrays, delegates that the programmer
  deals with via references
• Assemblies are essentially collections of type
  definitions
• Including all metadata about those types

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Type Metadata and the CLR

• Every CLR type has metadata associated with it
• Field names and sizes, type name, type size etc
• Used system-wide
• Serialization of objects to network, disk, in Web
  Services
• Cross-language interoperability
• Intellisense in Visual Studio
• We use it in our Grid Services software
• Possible to use Reflection API to access metadata
  at runtime
• Plug and play components, late binding
• Possible to define application-specific metadata
• Very useful, more later

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Metadata Addresses COM Shortcomings

• Type system was fragmented
• External representation of a component had little
  bearing on its internal structure
• Interface Definition could not tell you about
  internals
• Needed to use things called Type Libraries to
  store metadata separately
• .NET type system is common among all languages
• Common Type System
• C string C string VB.NET string

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CLR Standards and Implementations

• Open standard (ECMA)
• CLR will run on any Windows computer
• 95/98, ME, 2000
• Built in to XP
• Based on open standards
• Ports to Linux underway
• Mono, dotGNU
• Microsoft have a shared-source, cross-platform
  version known as Rotor
• Runs on FreeBSD
• http//msdn.microsoft.com/net/sscli

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Class Library (1/2)

• IO
• GUI Programming (naturally!)
• System Information
• Collections
• Components
• Application Configuration
• Connecting to Databases (ADO.NET)
• Tracing and Logging
• Manipulating Images/Graphics

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Class Library (2/2)

• Interoperability with COM
• Globalization and Internationalization
• Network Programming with Sockets
• Remoting
• Serialization
• XML
• Security and Cryptography
• Threading
• Web Services

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Language Compilers

• Over 20 different languages supported to date
• C, VB, C
• Perl, Python, Scheme, F, Fortran, J, write your
  own!
• All produce IL
• Cross-language compatibility is a feature of the
  runtime
• Write component in VB and use from C, C,
• Must adhere to the Common Language Specification
• Limits things you can use e.g. unsigned types,
  operator overloading

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Web Application Development

• ASP.NET provides a rich platform for developing
  Web applications and Web Services
• A huge leap forward from traditional ASP
• Aimed towards enterprise class,
  industrial-strength Web applications
• Fully integrated with all areas of .NET
• Our software is based on this framework

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Distributed Computing

• Remoting and Web Services allow remote procedure
  calls
• Remoting is used to make calls between .NET
  Application Domains
• Built-in to CLR
• Web Services are used to provide cross-platform
  RPC in an interoperable manner
• ASP.NET and CLR support

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Obtaining the Framework

• Download the Framework SDK via
• http//msdn.microsoft.com/netframework/
• 110 Mb
• Support at http//msdn.microsoft.com
• Visual Studio .NET is available at a reduced rate
  for academic institutions

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• .NET Programming with C

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C Features (1/2)

• Programming language of choice for the .NET
  platform
• Microsofts preferred language
• Java-like, but has much in common with C
• 70 Java, 10 C, 5 VB, 15 new
• Strongly-typed
• Enforced by the compiler and the runtime
• As are all .NET languages
• Object-oriented
• Every object is an instance of a particular Type
• Types are class, interface, enum, struct
• Single implementation inheritance, multiple
  interface inheritance a la Java

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C Features (2/2)

• Close coupling with managed code services
• Garbage collection, threading
• Operator overloading allowed
• C heritage
• Can access raw pointers using unsafe code blocks
• Properties are a first class language feature
• Unlike Java where accessor methods must be coded
• Syntactic sugar, but nice!
• Supports strongly-typed callback mechanisms
  directly using events/delegates
• Unlike Java, where callback support is indirect
  (interface based, anonymous inner classes etc)

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Really New C Features (compared to Java)

• Supports call by reference
• Use of out and ref keywords
• Supports stack-allocated objects (structs)
  Value Types
• Supports enumerations directly
• Can use as C/C style bit-mask/flags
• Explicit versioning control
• More a feature of the framework but accessible
  using C
• True multi-dimensional arrays
• More efficient
• Semi-deterministic finalization
• Using IDisposable

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Namespaces

• Means of dividing related classes logically
• Avoid name clashes
• Analogous to Java packages, C namespaces
• MyCompany.MyApplication.Module
• Declare using braces
• namespace MyNamespace // classes etc
• Import namespace with using directive
• using System.Xml
• Must include assembly where classes belonging to
  a namespace reside
• /reference command line option on csc (C
  compiler)
• Classes from a namespace do not have to all live
  in same assembly
• System namespace is root of .NET framework classes

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Sample Program

• //Person.cs
• using System
• using SomeLib
• namespace MyApplication
• class Person
• private string name_public string Name
  get return name_ set
  if(value null) throw
  new
• ArgumentNullException(name)
  name_ value
• public static void Main
• Person p new Person()
• p.Name Daragh Console.WriteLine(p.
  Name)

• Compile as follows
• Produces Person.exe
• C/gt csc Person.cs
• /referenceSomeLib.dll
• Execute
• C/gt person output Daragh

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Using C

• Very intuitive at first if you are a Java
  programmer
• Some differences will soon be noticed
• Command-line is good for learning
• csc.exe, vbc.exe, cl.exe
• Best way to use is with Visual Studio .NET
• Nice for GUI apps, great designer for forms, Web
  applications
• Integrates with source control (Source Safe)
• Good for large multi-component projects
• If you do not have it, there is always the
  command-line
• Good to know your way around this way

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Useful Things (1/2)

• Boxing and unboxing
• Primitive (value) types can be treated as
  reference types without explicitly wrapping them
• Java Integer I new Integer(5)
• C int i 5
  object o i o 1 // i
  5, o 6
• foreach
• foreach(element e in array)
• foreach(element e in somethingEnumerable)

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Useful Things (2/2)

• Exception safe casts using as
• Employee e new Employee()Person p e as
  Personif(p ! null)...
• Properties are integral
• Dont define field, accessor, setter
• Looks like field to clientpublic int
  MyProperty get // logic set myField_
  value x.MyProperty 2

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Attributes

• Can add custom metadata to your types
• public class SomeType
• WebMethod
• public string SomeMethod()