Microsoft .NET Basics
Daragh Byrne – EPCC
http://www.epcc.ed.ac.uk/~ogsanet
ogsanet-queries@epcc.ed.ac.uk
February 24th-25th 2004
Purpose
Microsoft .NET Framework:
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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:
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Win32/C-style APIs are outdated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
Compiled to
MSIL
Source Code (C#, VB.NET)
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 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
Bind to runtime library
.NET Executable
(Stored as Windows Portable
Executable file)
mscoree.dll
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:
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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:
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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 :
• C#
Integer I = new Integer(5);
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 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()
{
…
}
}
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