Get the Gist: .NET

Get the Gist:
.NET
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www.compass-point.net

History
• MS was on a path to embrace Java
as the technology for programming
its legacy component technology
COM. MS called it J++.
• Why MS developed .NET:
– Presumably because of lawsuit with
Sun, MS abandoned J++ but took
ideas learned from Java and made
them into .NET.
– MS wanted hardware independence
for coming mobile, cell, Xbox, and
other devices.
– C++/MFC wasn’t competitive against
new breed of languages (Java).
– Expensive to maintain multiple
development environments: Interdev,
C++, VB, etc.

Today
• .NET has virtually replaced
C++, MFC, and COM for new
development.
• Much of the Windows API is
exposed in .NET. Some aren’t
even exposed in other ways
any more.
• COM within Windows is now
gradually being replaced with
.NET components.

.NET Technologies
• .NET framework
• Windows Forms
• ASP.NET
• Enterprise Services
• .NET Compact
• Windows Services
• Web Services
• XML
• SQL Server

Common .NET terms
• CLR – common language
runtime.
• Assembly – a versioned and
signed .NET EXE or DLL.
• Global Assembly Cache
• Managed / unmanaged.
• IL – Intermediate language.

.NET Compilers
• MS ships C#, VB.NET, jscript, C++,
J++ as .NET languages.
• Many others have been developed
including Python (IronPython),
Haskell, Smalltalk, etc.
• Languages and compilers must
conform to the CLS, which
essentially defines IL.
• Language compilers compile from
language to a binary form of IL and
are ‘packaged’ in an assembly PE
exe or dll file.

How C# Looks
using genericCar;
namespace Toyota;
{
public class Camry : Car
{
private static Camry camry;
private Brake brake;
public void main()
{
camry = new Camry();
camry.getBrake().ToString();
}
public Camry()
{
this.brake = new Brake();
}
public override Brake getBrake()
{
return this.brake;
}
}
}
Camry.cs

C# continued
using System.IO;
namespace Toyota
{
public class Brake
{
string brakeName;
public Brake()
{
this.brakeName = “Brake 1”;
}
public override string ToString()
{
System.Console.Out.Writeln(“I’m ” +
this.brakeName);
}
}
}
Brake.cs

How VB.NET looks
Namespace GenericCar
Class Car
Public MustOverride Sub getBrake()
End Class
Car.vb

Assemblies
• Versioned
• Digitally signed.
• Configuration is in XML and
not in registry.
• XCopy deployment.
• Assemblies written in different
languages can integrate.
• Compiling results in the
following:

Visual Studio Solution
using genericCar;
namespace Toyota;
{
public class Camry : Car
{
private static Camry camry;
private Brake brake;
public void main()
{
Camry.cs
camry = new Camry();
camry.getBrake().ToString();
public Camry()
{
this.brake = new Brake();
public override Brake getBrake()
{
return this.brake;
using System.IO;
namespace Toyota
{
public class Brake
{
string brakeName;
public Brake()
{
Brake.cs
this.brakeName = “Brake 1”;
public override string ToString()
{
System.Console.Out.Writeln(“I’m ” +
this.brakeName);
PE/ COFF HEADER
CLR HEADER
CLR DATA
MetaData IL (code)
NATIVE IMAGE SECION
.data, rdata, .rsrc, .text
Project 1
Compile as: EXE
Language: C#
Reference: project 2.dlll
}
}
}
}
}
}
}
}
}
Project 2
Compile as: DLL
Language: VB.NET
Namespace GenericCar
Class Car
Public MustOverride Sub getBrake()
End Class
Car.vb
C# compiler
(C# -> IL assembly)
VB.NET compiler
(VB -> IL assembly)
Project 1.exe
assembly
Project 2.DLL
assembly
PE/ COFF HEADER
CLR HEADER
CLR DATA
MetaData IL (code)
NATIVE IMAGE SECION

CLR
• Windows program loader
invoked: new process space
set up.
• Windows program loader loads
.NET assembly PE exe.
• Windows program loader
detects CLR section in PE.
• Windows loads CLR
executable, passing it CLR IL
data as follows:

Project 1.exe
assembly
PE/ COFF HEADER
CLR HEADER
CLR DATA
MetaData IL (code)
NATIVE IMAGE SECION
CLR JIT COMPILER
(IL to native)
Class Loader
Verifier
Just in time compiler (JIT)
Generates Just
in Time (JIT)
Project 1.exe invoked
Windows PE program loader
Project 2.DLL
assembly
PE/ COFF HEADER
CLR HEADER
CLR DATA
MetaData IL (code)
NATIVE IMAGE SECION
Loads
Project
1.exe PE
Detects it is
a CLR PE.
Loads CLR
Determines
that project
2.DLL is
required:
locates and
loads
Process space
Native CPU executable code

.NET Framework
• Comprised of assemblies
stored in global assembly
cache.
• Accessible to all programs and
all programming languages.
• Are extremely similar to Java’s
class library.
• Are very thorough, intuitive –
they just work as they are
supposed to.
• All are classes that can be
extended or overridden.

.NET Languages
Features
• All use namespaces.
• All are derived from Object.
• Garbage collection.
• No globals.
• Main() in a class (like Java).
• Full exception handling support and
common error handling
mechanism.
• Single inheritance.
• Supports generics.
• Attributes
• Reflection.

A Perspective
• .NET code considered to perform
on par with compiled C++. Lags
optimized C.
• .NET applications tend to be far
more reliable and handle errors
better than traditional Windows C
and MFC applications.
• Speed of development over MFC >
5X in my experience.
• Helps developers retain their sanity
– far better framework than MFC.
It’s the way it always should have
been…
• Once you know .NET, you can code
in Java.

My favorite reference
.NET Framework Essentials, Thuan Thai & Hoang Q. Lam, O’Reilly.

Get the Gist: .NET

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