ADO.NET Fundamentals

ADO.NET

• ADO.NET (ActiveX Data Objects .NET) is a set of classes that provide data access services to .NET applications
• Allows connection to various data sources such as databases, files, and XML data
• Consists of two main components:
  • Connected Data Access: uses Connection and Command objects to interact with data sources
  • Disconnected Data Access: uses DataSet and DataTable objects to store and manipulate data in memory

Exception Handling

• Exception handling is a mechanism to handle runtime errors in VB.NET
• Try-Catch-Finally block:
  • Try: code that may throw an exception
  • Catch: code to handle the exception
  • Finally: code to execute regardless of whether an exception was thrown
• Types of exceptions:
  • SystemException: exceptions thrown by the .NET runtime
  • ApplicationException: exceptions thrown by the application
• Throw keyword: used to rethrow an exception or throw a new one
• Try-Catch block can be nested to handle different types of exceptions

Object-oriented Programming (OOP)

• OOP principles:
  • Encapsulation: hiding internal implementation details
  • Abstraction: showing only necessary information
  • Inheritance: creating a new class based on an existing one
  • Polymorphism: multiple forms of a class or method
• Class:
  • A blueprint for creating objects
  • Can contain properties, methods, and events
• Object:
  • An instance of a class
  • Has its own set of attributes (data) and methods
• Inheritance:
  • Base Class: the class being inherited from
  • Derived Class: the class that inherits from the base class
  • MustInherit: keyword to indicate a class cannot be instantiated
• Polymorphism:
  • Overloading: multiple methods with the same name but different parameters
  • Overriding: a derived class provides a different implementation of a method

ADO.NET

• ADO.NET is a set of classes that provide data access services to .NET applications
• Enables connection to various data sources such as databases, files, and XML data
• Comprises two main components:
  • Connected Data Access: utilizes Connection and Command objects to interact with data sources
  • Disconnected Data Access: utilizes DataSet and DataTable objects to store and manipulate data in memory

Exception Handling

• Exception handling is a mechanism to handle runtime errors in VB.NET
• Try-Catch-Finally block:
  • Try: code that may throw an exception
  • Catch: code to handle the exception
  • Finally: code to execute regardless of whether an exception was thrown
• SystemException: exceptions thrown by the .NET runtime
• ApplicationException: exceptions thrown by the application
• Throw keyword: used to rethrow an exception or throw a new one
• Try-Catch block can be nested to handle different types of exceptions

Object-oriented Programming (OOP)

• Encapsulation: hiding internal implementation details
• Abstraction: showing only necessary information
• Inheritance: creating a new class based on an existing one
• Polymorphism: multiple forms of a class or method
• Class: a blueprint for creating objects
• Object: an instance of a class with its own set of attributes (data) and methods
• Inheritance:
  • Base Class: the class being inherited from
  • Derived Class: the class that inherits from the base class
  • MustInherit: keyword to indicate a class cannot be instantiated
• Polymorphism:
  • Overloading: multiple methods with the same name but different parameters
  • Overriding: a derived class provides a different implementation of a method

Object-Oriented Programming (OOP)

• Classes define properties and behavior, while objects are instances of classes with their own state and behavior
• Classes act as blueprints for creating objects
• Objects can be thought of as instances of classes

Inheritance

• Inheritance allows a child class to inherit properties and behavior from a parent class (also known as the base class)
• Child classes can build upon the properties and behavior of parent classes
• Inheritance enables code reuse and facilitates a more hierarchical organization of code

Polymorphism

• Polymorphism enables objects to take on multiple forms
• Method overriding allows for providing a different implementation for a method
• Method overloading allows for providing multiple definitions for a method
• Polymorphism enhances flexibility and modularity in programming

Encapsulation

• Encapsulation involves hiding internal implementation details from the outside world
• Encapsulation promotes information hiding and abstraction
• Public methods and properties are used to expose only necessary information

Abstraction

• Abstraction involves focusing on essential features and hiding non-essential details
• Abstraction enables defining an interface or abstract class to provide a contract
• Abstraction facilitates modular and reusable code

ADO.NET

ADO.NET Components

• Connection establishes a connection to a database
• Command executes a SQL query or stored procedure
• DataReader retrieves data from a database in a read-only, forward-only stream
• DataAdapter fills a DataSet with data from a database and updates the database

DataSet

• DataSet is an in-memory representation of data
• DataSet can be used to store and manipulate data locally
• DataSet can be updated and synchronized with a database

Data Binding

• Data binding involves binding data to a control or component
• Data binding automatically updates the control when the data changes
• Data binding facilitates a loose coupling between data and its presentation

Exception Handling

Try-Catch Blocks

• Try block contains code that may throw an exception
• Catch block contains code that handles the exception
• Finally block contains code that runs regardless of whether an exception was thrown

Exception Types

• System.Exception is the base class for all exceptions
• ApplicationException is the base class for custom exceptions
• Specific exceptions (e.g., SqlException, IOException) inherit from these base classes

Throwing Exceptions

• The Throw keyword is used to manually throw an exception
• The Throw keyword can be used to rethrow an exception
• Throwing exceptions facilitates error handling and debugging

Best Practices

• Catch specific exceptions rather than general exceptions
• Avoid catching exceptions that cannot be handled
• Use finally blocks to release resources
• Follow best practices for exception handling to ensure robust and reliable code