C# AND .NET
FRAMEWORK
By
Dr. Hemavathi P
Associate Professor
Dept. of CSE, BIT
hemavathiruchith@gmail.com
Books for Reference
 The Complete Reference: C# 4.0
 By Herbert Schildt

Tata McGraw Hill, 2012.
 Professional C# 2012 with .NET 4.5
 By Christian Nagel et al.
 Wiley India, 2012
Dr. Hemavathi P, B I T
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Chapter - 1
The Philosophy of .NET
Dr. Hemavathi P, B I T
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Objectives
• Understanding the previous state of
affairs
• The .NET Solution
• Building blocks of .NET Platform
 CLR, CTS, and CLS
• .NET Base Class Libraries
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Understanding the
previous state of affairs
• As a C/Win32 API Programmer
It is complex
C is a short/abrupt language
Manual memory management, ugly pointer
arithmetic, ugly syntactic constructs
 Not a OO language
As a C++/MFC Programmer
 Root is C
 C++ with MFC is still complex and error-prone
As a VB 6 Programmer
 Not a complete OOP (“Object-aware”) – Why?
 Doesn’t support inheritance
 No multithreading
 No parameterized Classes
 Low-level API calls are complex

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•
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Previous state of affairs…
• As a Java/J2EE Programmer




Use of Java front-to-back during development
cycle
No language freedom!
Pure Java is not suitable for graphic intensive
problems (E.g. 3D game)
No cross-language integration
• As a COM Programmer




Complex creation of COM types
Active Template Library (ATL)
Forced to contend with brittle/fragile registration
entries
Deployment issues
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.NET Solution
• Full interoperability with existing Win32 Code

Existing COM binaries can interoperate with .NET binaries

Supports cross-language inheritance, exception handling, and
debugging
• Complete and total language integration
• Common runtime engine shared by all .NET aware
•
languages
A base class library

Good object model used by all .NET aware languages

No IClassFactory, IUnKnown, IDispatch, etc.


No need to register a binary unit into the system registry
Allows multiple versions of same *.dll
• No more COM plumbing!
• Truly simplified deployment model
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.NET Framework
VB
C++
C#
JScript
J#
Common Language Specification
Windows
Forms
ADO.NET and XML
Base Class Library
Visual Studio.NET
ASP.NET
Web Forms Web Services
Common Language Runtime
Operating System
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Building Blocks of .NET
• CLR (Common Language Runtime)


To locate, load, and manage .NET types
Automatic memory management, language
integration, and type safety
• CTS (Common Type System)

Describes all possible data types and
programming constructs supported by the
runtime
• CLS (Common Language Specification)

A set of rules that defines a subset of types and
specifications
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CLR
•
•
•
•
•
•
•
•
(Common Language Runtime)
CLR sits on top of OS (same as JVM of Java)
CLR loads modules containing executables and executes
them
Code may be managed or unmanaged
Managed code consists of instructions in pseudo random
code called CIL (Common Intermediate Language). CIL
instructions are JIT compiled into native machine code at
runtime
JIT compiled methods reside in cache until the application’s
life time
Advantages of managed code: type safety, memory
management, and code verification security
CLR can translate code from C#, J#, C, C++, VB, and
Jscript into CIL.
CLR doesn’t launch a new process for every application. It
launches one process and hosts individual applications in
application domains
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Base Class Libraries
• Encapsulates various primitives like: threads, file
•
IO, graphical rendering, and other interaction with
HW devices
It also provides: database manipulation, XML
integration, Web-enabled front-end.
Data Access
GUI
Threading
File IO
Base Class Libraries
XML/SOAP
Common Language Runtime
CLS
CTS
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C#
•
•
•
•
•
•
•
Almost same as Java
No pointers required
Automatic memory management (No ‘delete’)
Enumeration, class, structure, etc.
Operator overloading allowed
Interface-based programming techniques
Assign characteristics to types (same as COM
IDL)
• C# can produce code that can run only on .NET
environment (unlike COM server or Win32 API)
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Understanding Assemblies
• Windows applications have dependencies
•
•
•
•
•
on one or more DLLs
These DLLs may contain COM classes
registered in System registry
When these components are updated,
applications may break – 'DLL hell'
Solution: .NET Assemblies
C# .NET compiler doesn't generate
machine code.
It is compiled into "assembly"
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Assembly
C# source code
+
Metadata
C# .NET Compiler
=
IL
Assembly
• Intermediate Language (IL/CIL):
Same as first pass of compiler. It can't be executed
(it is not in binary format)
Metadata
 Describes the assembly contents
 No need for component registry
 Each assembly includes information about references
to other assemblies
 E.g. If you have a class called Car in a given
assembly, the type metadata describes Car's base
class, which interfaces are implemented by Car,
description of members of Car.

•
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Assembly…
• When CLR loads your application, it examines your
•
•
•
program's metadata to know which external
assemblies are required for execution
Private assemblies
 Used by single application
 Is not shared
 Most preferred method
Shared assemblies
 Intended for multiple applications
 Global Assembly Cache
Manifest
 The metadata of assemblies: version, list of
externally defined assemblies, etc.
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Example of CIL
•
•
CIL sits above a specific compiler
(C#, J#, etc.)
The associated compiler emits CIL
instructions
using System;
namespace Calculator
{
}
public class CalcApp
{
}

public static void Main(string[] args)
{
Calc c = new Calc();
int ans = c.Add(10, 84);
Console.WriteLine(ans);
Console.ReadLine();
}
Dr. Hemavathi P, B I T
public class Calc
{
public int Add(int x, int y)
{ return x + y; }
}
All .NET aware languages
emit same CIL instructions
16
CIL of Add() Method
.method public hidebysig instance int32 Add(int32 x,
int32 y) cil managed
{
// Code size
8 (0x8)
.maxstack 2
.locals init ([0] int32 CS$00000003$00000000)
IL_0000: ldarg.1
IL_0001: ldarg.2
IL_0002: add
IL_0003: stloc.0
IL_0004: br.s
IL_0006
IL_0006: ldloc.0
IL_0007: ret
} // end of method Calc::Add
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Manifest
External
Assembly
.assembly extern mscorlib
{
.publickeytoken = (B7 7A 5C 56 19 34 E0 89 )
.ver 1:0:5000:0
}
.assembly ConsoleApplication1
{
// .z\V.4..
.hash algorithm 0x00008004
.ver 1:0:2058:39833
}
.module ConsoleApplication1.exe
// MVID: {51BE4F31-CBD0-4AE6-BC9D-F9A4976795FD}
.imagebase 0x00400000
.subsystem 0x00000003
.file alignment 4096
.corflags 0x00000001
// Image base: 0x070b0000
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CIL to Execution
Desktop
CIL
JIT
Server
Pocket PC
• Jitter compiles CIL instructions on the fly
into corresponding machine code and cache
it. This is useful for not recompiling, if the
same method is called again
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Common Type System (CTS)
• CTS is a formal specification that
•
•
•
•
•
describes how a given type must be
defined for CLR
CTS Class Type
CTS Structure Type
CTS Interface Type
CTS Enumeration type
CTS Delegate type
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CTS Class Type
• Same as C++ class
• Can contain members: methods,
properties, events, etc.
• Support for abstract members that
define a polymorphic interface for
derived classes
• Multiple inheritance is not allowed
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CTS Class Characteristics
• "sealed"? – sealed classes can't function
as base classes
• Implement any interfaces? – An
interface is a collection of abstract
members
• Abstract or Concrete? – Abstract classes
(to define common behaviors for derived)
can't be created directly but concrete
classes can.
• Visibility? – visibility attribute to know
whether external assemblies can use it.
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• CTS Structure types
•
 Same as C/C++
Derived from a common base class
System.ValueType
• CTS Enumeration type


To group name/value pairs under a specific name
Default Storage: System.Int32 (could be
changed)
• CTS Interface Type

Same as pure abstract class of C++
A description of work that a derived class can
perform
Similar to a class, but can never be instantiated


Same as C's function pointer (System.MulticastDelegate)
Useful for event handling (ASP .NET)


• CTS Delegate type
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Intrinsic CTS Data Types
.NET Base Type
C# Type
System.Byte
Byte
System.SByte
sbyte
System.Int16
short
System.Int32
int
System.Int64
long
System.UInt64
ulong
System.Single
float
System.Double
double
System.Object
object
System.String
string
System.Boolean
bool
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Common Language Specification
(CLS)
• Set of guidelines that describe the minimal
and complete set of features a given .NET
aware compiler must support
• C# uses + for concatenation whereas VB
.NET uses &
• C# allows operator overloading but VB .NET
does not!
• The void functions may differ in syntax:
' VB .NET
// C#
Public Sub Foo()
'…….
End Sub
public void Foo()
{ ……. }
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CLS Compliance
C# Type
CLS Compliance
byte
Yes
sbyte
No
short
Yes
int
Yes
long
Yes
ulong
No
float
Yes
double
Yes
object
Yes
string
Yes
char
Yes
bool
Dr. Hemavathi
P, B I T
Yes
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Example
public class Calc
{
// CLS compliant
public int Add(int x, int y)
{ return x + y; }
}
// Not CLS compliant
public ulong Add(ulong x, ulong y)
{ return x + y; }
• Once a method is CLS compliant, then all the
.NET aware languages can interact with that
implementation
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CLR
.NET Compiler
.NET
Source
Code
DLL or EXE
(CIL)
mscoree.dll
Class Loader
Base Class
Libraries
(mscorlib.dll)
Jitter
Platform
Specific code
mscoree.dll
MicroSoft Common
Object Runtime Execution Engine
Execute
.NET Execution Engine
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.NET Namespace
• MFC, Java, VB 6.0 have predefined
set of classes; C# doesn't
• C# uses namespace concept
• Any language targeting the .NET
runtime makes use of the same
namespaces and same types as C#
• System is the root namespace
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Example in C#
System Namespace
using System;
public Class MyApp
{
public static void Main() Console class in
System Namespace
{
Console.WriteLine("Hello World");
}
}
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Example in VB .NET
Imports System
Public Module MyApp
Sub Main()
Console.WriteLine("Hello World")
End Sub
End Module
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Example in Managed C++
#using <mscorlib.dll>
using namespace System;
void Main()
{
Console::WriteLine("Hello World");
}
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Sample .NET namespaces
System
primitive types, garbage
collection, etc
System.Collections
Container objects: ArrayList,
Queue, etc.
System.Data
System.Data.Common
System.Data.OleDb
System.Data.SqlClient
For Database manipulations
ADO .NET
System.IO
file IO, buffering, etc.
System.Drawing
System.Drawing.2D
GDI+ primitives, bitmaps, fonts,
icons, etc.
System.Threading
Threads
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Demo
• Console Application
• Windows Application
• Graphics
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End of Chapter 1
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