microsoft .net basics

http://www.epcc.ed.ac.uk/~ogsanet

ogsanet-queries@epcc.ed.ac.uk

February 24th-25th 2004

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• Win32/C-style APIs are outdated• COM was step in right direction, but painful to program with• COM was restricted to VB, C++• Binary compatibility/portability an issue: x86 version of COM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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What’s in the .NET Framework?

Microsoft Intermediate Language (MSIL):– Specification for a platform independent, low-level, stack-based assembly-like

language

Common Language Runtime (CLR):– A common runtime for all .NET applications, compiles and executes MSIL

Class libraries:– Common functionality that can be used by all languages

– Includes Windows Forms for GUI development

Language compilers:– C#, C++, VB…

Distributed computing:– Networking using sockets, Remoting, Web Services and Applications using

ASP.NET

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Targeting .NET

Source Code (C#, VB.NET) MSIL

CLR

Native Code (x86 etc)

Compiled to

Runs on

Compiled to

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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 CS$00000003$00000000)

IL_0000: ldarg.0 IL_0001: ldfld string NDoc.Core.HtmlHelp::_projectName IL_0006: ldstr ".hhk“ IL_000b: call string [mscorlib]System.String::Concat(string,

string) IL_0010: stloc.0 IL_0011: br.s IL_0013 IL_0013: ldloc.0 IL_0014: ret

Yuck! Thankfully we don’t have to deal with this:

– That’s 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:– Microsoft’s 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:/> csc Person.cs

/reference:SomeLib.dll

Execute:– C:/> 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 asEmployee e = new Employee()Person p = e as Person;if(p != null){...}

Properties are integral:– Don’t define field, accessor, setter– Looks like field to client:public 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() { …

}

}