NameSpace is the Logical group of types or we can say namespace is a container (e.g Class, Structures, Interfaces, Enumerations etc.).

Example: a) System.IO logically groups input output related features.

b) System.Data.SqlClient is the logical group of ado.net Connectivity with Sql server related features. In Object Oriented world, many times it is possible that programmers will use the same class name, Qualifying NameSpace with class name can avoid this collision.

virtual method
A virtual method can be redefined. The virtual keyword designates a method that is overridden in derived classes.
A virtual method is created in the base class that can be overriden in the derived class.
Override Method
The override modifier is needed for implementing polymorphic behaviors in derived classes. You can re-implement a virtual base method. This causes the base implementation to be ignored in favor of the override method.

Abstract Class
Abstract classes, marked by the keyword abstract in the class definition, are typically used to define a base class in the hierarchy. What’s special about them, is that you can’t create an instance of them – if you try, you will get a compile error.

Abstract method
An abstract method has no implementation. Its implementation logic is provided instead by classes that derive from it. We use an abstract class to create a base template for derived classes.

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Classes: Class is a C# construct to model real-world objects into classes

Exa:
class Employee
{
private string _name;
private char _gender;
private string _qualification;
private uint _salary;
}

Access Modifiers

• Public:Accessible to the members of the containing class as well as non-members of the class
• Private:Accessible only to the members of the containing class
• Protected:Accessible to the containing class or types derived from the containing class

Constructors: Special method of a class that is called every time an instance of the class is created

Exa:
Employee()
{
qualification = “Graduate”;
}

Destructor: Special method to perform cleanup operations

Syntax:

{
body of destructor
}

Note:

• Methods can be overloaded on the basis of varying number of parameters or different data types.
• Namespace consists of a group of related classes
• Inheritance is the process of acquiring features of an existing class.
• The class based on which the new class is created is called base class or parent class and the class that is created is called derived, sub or child class.
• The keyword base is used to access members of the base class from inside a derived class.
• The override keyword is used to modify a method, property or an indexer.
• The new modifier is used to explicitly hide a member that is inherited from the base class.
• Abstract Classes are classes that contain at least one abstract member (method without implementation).
  Abstract class cannot be instantiated.
• Overriding a method is to change the implementation of the method in the derived class.
• The virtual keyword is used to modify the declaration of a method.
• Explicit Interface Implementation is used to specify which interface a member function is implementing in case of a name ambiguity.

Namespcace, virtual method, abstract method

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Variables: Variables are used to store values of a particular datatype.

Syntax:
access_modifier datatype VariableName

Constants: Constants are used to maintain a value throughout a program.

Syntax:
const datatype ConstantName = value;

Fundamental Types Of C#

C# divides data types into two fundamental categories

Value Types
Represent actual data
Just hold a value in memory
Are stored in a stack
int, char, structures

Reference Types
Signify a pointer or a reference to the data
Contains the address of the object in the heap
= null means that no object has been referenced
classes, interfaces, arrays, strings

Data types in C#

Boxing & Unboxing
Boxing is conversion of a value type into a reference type

Unboxing is the conversion of a reference type into a value type

With Boxing and unboxing one can link between value-types and reference-types by allowing any value of a value-type to be converted to and from type Object.

• Operators in C#Arithmetic
• Comparison
• Ternary (Conditional)
• Assignment
• Logical

Iteration Constructs
To perform a set of instructions for a certain number of times or while a specific condition is true.

Types of iteration constructs –
The While Loop
The Do Loop
The For Loop
The foreach Loop
Arrays
A group of values of similar data type
Belong to reference type and hence arrays are stored on the heap
The initialization or assigning of values to the array elements can be done when it is declared or at a later stage in the program.
Syntax:
DataType [number of elements] ArrayName;
exa : int[4] array1;
Structures
Custom data Types
Can have methods defined within them
Cannot implement inheritance
Represent Value types

exa:

struct student
{
public int stud_id;
public string stud_name;
public float stud_marks;

public void show_details()
{
//display student details
}

Enumerators
Enums (abbreviation for Enumerators) are a set of named numeric constants.
Used to define a data type that can have a specific set of values
Enumerators are defined using the keyword enum.

exa:
public enum WeekDays
{
Monday=1,
Tuesday=2,
Wednesday=3,
Thursday=4,
Friday=5
}

Object oriented programming with c#

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The .NET Framework defines the environment to execute Visual C# .NET applications and the services you can use within those applications.

The .NET Framework has two main components:

•  Common Language Runtime (CLR)
•  A unified set of class libraries

The .NET class libraries include code for programming topics such as threading, file I/O, database support, XML parsing, and data structures.

In addition to CLR and class libraries, the .NET framework also includes the programming languages and ASP.NET.

CLR and MSIL

CLR ensures that the functionality available to one language is available to any other .NET language.

Microsoft Intermediate Language (MSIL) is composed of a specific set of instructions that indicate how your code should be executed.

The main job of a JIT compiler is to translate your generic MSIL code into machine code that can be directly executed by your CPU.

MSIL code can be easily read by the verification process

CLS,CTS & Garbage Collector

• Common Language Specification (CLS)
• Is a set of rules that any .NET language should follow
• Is used to create applications that are interoperable with other languages

Common Type System (CTS) commonly:

• Contains the standard data types
• Contains the set of guidelines.

Garbage Collector

•  Is a destructor used for clean up operations
•  Is responsible for freeing up memory

Conclusion

• .NET Framework is made up of two major components; .NET Framework Class Library and Common Language Runtime.
• The CLR is a modern runtime environment that manages the execution of user code, providing services such as JIT compilation, memory management, exception management, debugging etc.
• The CTS defines the rules by which all types are declared, defined and managed, regardless of source language.
• The CLS is a set of minimum standards that all compilers targeting .NET must support to ensure language interoperability.
• Namespaces is a grouping of similar classes having related methods and is used specifically to avoid name clashes between classes.
• The Just In Time (JIT) compiler compiles the MSIL code into a native code that is specific to the OS and machine architecture being targeted.

Basic Data Types in C#

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Steps to connect sql server database using c#. net

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