Advantages of .NET over the other languages, overview of .NET binaries, Intermediate Language, metadata, .NET Namespaces, Common Language runtime, common type system, common Language Specification. C# fundamentals – C# class, object, string formatting, Types, scope, constants, C# iteration, control flow, operators, array, string, Enumerations, structures, custom Namespaces

1. 1
C # and .Net Technologies
Advantages of .NET over the other languages
The .Net Framework offers a number of advantages to developers.
Below are few advantages of .Net Framework:
1. Consistent programming model : With .Net accessing data with a C# and VB.Net very similar
apart from slight syntactial differeneces. Both the programs need to import the System.Data
namespace, both programs establish connection with database and both programs run a
query and display the data.
2. Direct Support for Security : .Net framework enables the developer and the system
administrator to specify method level security.
3. Simplified Development efforts: The .Net Framework simplifies debugging with support for
Runtime diagnostics.
4. Easy application deployment and Maintenance : The .Net Framework makes easy to deploy
applicaitons.The .Net Framework handles the details of locating and loads the components.
5. Assemblies : Assembly is elementary unit in a framework application. It performs various
functions in programming with the .Net Frame work. Every computer that has the .Net
Framework installed with have the Global Assembly Cache.
Overview of .NET binaries
 .NET binaries take the extension of .dll
 .NET binaries do not contain platform-specific instructions, but rather platform-
agnostic intermediate language (IL) and type metadata.
 When a *.dll or *.exe has been created using a .NET-aware compiler, the resulting
module is bundled into an assembly.
Note: An assembly is a collection of types and resources that are built to work together and form a logical unit
of functionality

2. 2
Intermediate Language
 CIL(Common Intermediate Language) is a language that sits above any particular
platform-specific instruction set. Regardless of which .NET-aware language you
choose, the associated compiler emits CIL instructions
 For example, C# compiler emits CIL, not platform-specific instructions
Benefits of CIL:
 One benefit is language integration. .NET-aware compiler produces nearly identical
CIL instructions. Therefore, all languages are able to interact within a well-defined
binary arena
 .NET allows you to build applications using your language of choice
Metadata
 In addition to CIL instructions, a .NET assembly contains full, complete, and accurate
metadata
 Metadata describes each and every type (class, structure, enumeration, and so forth)
defined in the binary, as well as the members of each type (properties, methods, events, and
so on).
 It is always the job of the compiler to generate latest metadata.
.NET Namespaces
 C# language does not come with a language-specific code library. Rather, C# developers
leverage the language-neutral .NET libraries.
 A namespace is a grouping of related types contained in an assembly. For example, the
System.IO namespace contains file I/O related types, the System.Data namespace defines
basic database types, and so on
 Any language targeting the .NET runtime makes use of the same namespaces and same
types.
Accessing a Namespace Programmatically
// Explicitly list the namespaces used by this file.
using System;
using System.Drawing;
class MyApp {
public void DisplayLogo() {
// Create a 20_20 pixel bitmap.
Bitmap companyLogo = new Bitmap(20, 20);
...
} }

3. 3
Building block of .NET
Common Language runtime, common type system, common Language Specification
Note: In the world of .NET, “type” is simply a generic term used to refer to a member from the set {class,
structure, interface, enumeration, delegate}
Common Type System (CTS)
 CTS is a formal specification that documents how types must be defined in order to be
hosted by the CLR
 Five types defined by the CTS:
1. CTS Class Types
2. CTS Structure Types
3. CTS Interface Types
4. CTS Enumeration Types
5. CTS Delegate Types
Common Language Specification
 Different languages express the same programming constructs in unique, language specific
terms, for example, in c# for Concatenation we use ‘+’ operator, while in VB.NET we use ‘&’.
Yet, respective compilers (csc.exe or vbc.exe, in this case) emit a similar set
of CIL(Common Intermediate Language) instructions.
 The Common Language Specification (CLS) is a set of rules that describe in vivid detail the
 minimal and complete set of features a given .NET-aware compiler must support to produce
code that can be hosted by the CLR.
 The CLS is ultimately a set of rules that compiler builders must conform to, if they intend
their products to function seamlessly within the .NET universe.
Common Language Runtime
 Term runtime can be understood as a collection of external services that are required to
execute a given compiled unit of code.
 .NET runtime provides a single well-defined runtime layer that is shared by all languages and
platforms that are .NET-aware
 The runtime engine is responsible for a number of tasks:
 Firstly, it is the entity in charge of resolving the location of an assembly and finding the
requested type within the binary by reading the contained metadata.
 The CLR then lays out the type in memory, compiles the associated CIL into platform-
specific instructions, performs any necessary security checks, and then executes the
code in question.
Note: An assembler is a program that takes basic computer instructions and converts them into a pattern of bits that the
computer's processor can use to perform its basic operations. Some people call these instructions assembler language and
others use the term assembly language.
Eg: L 8,3000
Means: Load the contents of memory location 3000 into Register 8.

4. 4
C# Fundamentals
C# classes & Objects
Defining Classes and Creating Objects
A class is a definition for a user-defined type.
An object is simply a term describing a given instance of a particular class in memory.
Eg:
using System;
class HelloClass {
public static int Main(string[] args) {
// You can declare and create a new object in a single line...
HelloClass c1 = new HelloClass();
// ...or break declaration and creation into two lines.
HelloClass c2;
c2 = new HelloClass();
...
} }
Default Values of Class Member Variables
 Boolean types are set to false.
 Numeric data is set to 0 (or 0.0 in the case of floating-point data types).
 String types are set to null.
 Char types are set to '0'.
 Reference types are set to null.
String Formatting
The C# string keyword is a shorthand notation of the System.String type, which provides a
number of members you would expect from such a utility class

5. 5
Types
There are basically 5 types in c#.
1. Classes
2. Structures
3. Interfaces
4. Enumerations
5. Delegates
Structures
A struct type is a value type that is typically used to encapsulate small groups of related
variables, such as the coordinates of a rectangle or the characteristics of an item in an
inventory
public struct Book
{
public decimal price;
public string title;
public string author;
}
The objects of a strcut can be created by using the new operator as follows.
book myBooks = new book();
The individual members of a struct can be accessed by using the dot (.) operator as showing
below.
myBooks.title= “who cares”;
myBooks.author = “Walking Stone”;
Interface
 An interface contains only the signatures of methods, properties, events or indexers.
 A class or struct that implements the interface must implement the members of the
interface that are specified in the interface definition
interface ISampleInterface {
void SampleMethod();
}
class ImplementationClass : ISampleInterface {
// Explicit interface member implementation:
void ISampleInterface.SampleMethod() {
// Method implementation.
}
Public static void Main() {
// Declare an interface instance.
ISampleInterface obj = new ImplementationClass();
// Call the member.
obj.SampleMethod(); } }

6. 6
Enumerations
The enum keyword is used to declare an enumeration, a distinct type that consists of a set
of named constants called the enumerator list.
By default, the first enumerator has the value 0, and the value of each successive
enumerator is increased by 1. For example, in the following enumeration, Sat is 0, Sun is 1,
Mon is 2, and so forth.
enum Days {Sat, Sun, Mon, Tue, Wed, Thu, Fri};
Enumerators can use initializers to override the default values, as shown in the following
example.
enum Days {Sat=1, Sun, Mon, Tue, Wed, Thu, Fri};
Delegates
 A delegate is a type that represents references to methods with a particular parameter
list and return type
 When you instantiate a delegate, you can associate its instance with any method with a
compatible signature and return type. You can invoke (or call) the method through the
delegate instance
public delegate int PerformCalculation(int x, int y);
Delegates have the following properties:
 Delegates are like C++ function pointers but are type safe.
 Delegates allow methods to be passed as parameters.
 Delegates can be used to define callback methods.
 Delegates can be chained together; for example, multiple methods can be called on
a single event.
Scopes
The scope of a name is the region of program text within which it is possible to refer to the entity
declared by the name without qualification of the name
 The scope of a namespace member declared by a namespace-member-declaration with no
enclosing namespace-declaration is the entire program text.
 The scope of a parameter declared in a constructor-declaration is the constructor-initializer
and block of that constructor-declaration.
 The scope of a local variable declared in a local-variable-declaration is the block in which the
declaration occurs.
 The scope of a local variable declared in a switch-block of a switch statement is the switch-
block.
 The scope of a local variable declared in a for-initializer of a for statement is the for-
initializer, the for-condition, the for-iterator, and the contained statement of the for
statement.
 The scope of a parameter declared in a method-declaration is the method-body of that
method-declaration.
 The scope of a member declared by a struct-member-declaration is the struct-body in which
the declaration occurs.
 The scope of a member declared by an enum-member-declaration is the enum-body in
which the declaration occurs.

7. 7
Constants
 Constants are immutable(unchanging over time) values which are known at compile
time and do not change for the life of the program.
 Constants are declared with the const modifier.
 Only the C# built-in types(eg, int, float, string etc) may be declared as const.
Eg:
class Calendar
{
const int months = 12, weeks = 52, days = 365;
}
C# iteration
The following keywords are used in iteration statements:
 do
 for
 foreach
 while
foreach: The foreach statement repeats a group of embedded statements for each element in an
array or an object collection
Control Flow
 if
 switch
 break
 continue
Operators
 Arithmetic Operators( +, -, *, /, %, ++, --)
 Relational Operators (==, !=, >, <, >=, <= )
 Logical Operators (&&, ||, !)
 Bitwise Operators (&, |, ^, ~, <<, >>)
 Assignment Operators (==, +=, -=, *=, /=, %=, <<=, >>=, &=, ^=, |=)
 Misc Operators (sizeof(), typeof(), &-returns address of variable, *-pointer, ?: , is, as)
Arrays
C# arrays can be divided into 4 categories:
1. Single-dimensional arrays
2. Multidimensional arrays or rectangular arrays
3. Jagged arrays
4. Mixed arrays.

8. 8
1. Single-dimensional arrays:
int[] myNum = new int[3] {1, 3, 5};
string[] strArray = new string[5] { "Mahesh", "Mike", "Raj", "Praveen", "Dinesh" };
2. Multidimensional arrays or rectangular arrays:
A multi-dimensional array, also known as a rectangular array is an array with more than one
dimension. The form of a multi-dimensional array is a matrix.
int[,] numbers = new int[3, 2] { { 1, 2 }, { 3, 4 }, { 5, 6 } };
string[,] names = new string[2, 2] { { "Rosy", "Amy" }, { "Peter", "Albert" } };
We can also initialize as :
int[,] numbers = new int[3, 2];
numbers[0, 0] = 1;
numbers[1, 0] = 2;
3. Jagged arrays
Jagged arrays are arrays of arrays. The elements of a jagged array are other arrays.
For example, the following code snippet declares a jagged array that has three items of an
array.
int[ ][ ] intJaggedArray = new int[3][ ];
Initializing jagged arrays:
intJaggedArray[0] = new int[2];
intJaggedArray[1] = new int[4];
intJaggedArray[2] = new int[6];
We can also initialize as:
intJaggedArray[0] = new int[2]{2, 12};
intJaggedArray[1] = new int[4]{4, 14, 24, 34};
intJaggedArray[2] = new int[6] {6, 16, 26, 36, 46, 56 };
Accessing Jagged arrays:
Console.Write(intJaggedArray3[0][0]);
4. Mixed arrays
Mixed arrays are a combination of multi-dimension arrays and jagged arrays. The mixed
arrays type is removed from .NET 4.0.

9. 9
Strings
 A string is an object of type String whose value is text.
 Internally, the text is stored as a sequential read-only collection of Char objects.
 There is no null-terminating character at the end of a C# string;
string name=”David”;
String escape sequences
t - Horizontal tab
v - Vertical tab
- Backslash
' - Single quote
" - Double quote
n - New line
Custom Namespaces
Custom namespace allows us to define our own namespaces and import them
into another program or application.
Eg:
// addtionlib.cs
using System;
namespace MyAddition
{
class addit{
………
}
}
myprogram.cs
using System;
using MyAddition //importing user-defined namespace
namespace myprogram
{
…….
}
}