Visual Basic Form Design and User Interface

• Visual Basic (VB) evolved from the earlier DOS version called BASIC and is a high-level language
• VB was designed for ease of use and learning
• VB enables quick creation of Windows desktop applications with GUIs

Form Design and User Interface

• A form, serving as the application’s user interface, is a window
• Forms include controls like buttons, text boxes, labels and list boxes
• Setting properties such as size, color, text, and position customizes forms
• The VB IDE provides a drag-and-drop interface for form design
• Double clicking a control on the toolbox adds it to the active form
• Controls are manipulated via mouse on the form
• Appearance of controls is defined by properties
• Behavior of controls is defined by code
• Controls are positioned, added, and configured to create the desired interface
• Common form controls:
  • Button: Triggers event when clicked
  • Label: Displays static text
  • TextBox: Allows user text entry
  • ListBox: Displays a list of items
  • ComboBox: Drop-down list of items
  • CheckBox: Allows users to select/deselect an option
  • RadioButton: Allows selection of one option from a group
  • PictureBox: Displays image
  • Timer: Executes code at specified intervals
• Events are actions, like button clicks or text changes, that occur on a control
• Event handlers are code blocks that execute in response to events
• Application behavior is determined by event handler code
• Controls respond to events, including mouse clicks, key presses, and value changes
• Each event is linked to a Subroutine, containing code that dictates event response
• Common events:
  • Click: Occurs when a control is clicked
  • TextChanged: Occurs when TextBox text changes
  • SelectedIndexChanged: Occurs when a ListBox or ComboBox selection changes
  • Load: Occurs when a form is loaded
  • KeyPress: Occurs when a key is pressed
• UI Principles:
  • Simplicity: Keep the UI easy to understand and clean
  • Consistency: Use consistent controls, layout, and terminology
  • Clarity: Make purpose of each control clear
  • Feedback: Provide feedback to the user in response to actions
  • Error prevention: Prevent errors by providing validation and clear instructions

Object-Oriented Concepts

• Object-oriented programming (OOP) is a paradigm based on objects
• Objects have data via fields/attributes/properties
• Objects contain code in the form of procedures/methods
• VB.NET is an object-oriented language
• Key OOP concepts:
  • Encapsulation: Bundling data and methods that operate on that data within a class
  • Abstraction: Simplifying complex reality by modeling classes appropriate to the problem
  • Inheritance: Creating new classes (derived classes) from existing classes (base classes)
  • Polymorphism: The ability of an object to take on many forms
• Class: A blueprint for creating objects
• Object: An instance of a class
• Properties: Attributes describing object characteristics
• Methods: Actions an object can perform
• Encapsulation:
  • Hiding internal implementation details of a class
  • Exposing only the necessary interface to the outside world
  • Achieved through access modifiers (e.g., Public, Private, Protected)
• Abstraction:
  • Representing essential features without including background details or explanations
  • Focusing on what an object does rather than how it does it
• Inheritance:
  • Enables new objects to take on the properties of existing objects
  • Creating a hierarchy of classes
  • Promoting code reuse and reducing redundancy
• Polymorphism:
  • The ability of an object to take on many forms
  • Achieved through method overloading and method overriding
  • Method overloading: Defining multiple methods with the same name but different parameters
  • Method overriding: Redefining a method in a derived class to provide a specific implementation

Procedural Programming

• Programming paradigm of procedures (subroutines/functions) is procedural programming
• Procedures are code blocks performing specific tasks
• Programs are structured as sequence of procedure calls
• Code is written in a sequence of instructions
• Variables store data
• Program flow is controlled by control structures, like loops and conditionals
• VB supports procedural programming concepts
• Variables: Named storage locations that hold data
  • Data types: Integer, Double, String, Boolean, Date, etc.
  • Variable declaration: Dim variableName As DataType
• Operators: Perform operations on data
  • Arithmetic operators: +, -, *, /, \ (integer division), Mod (modulus)
  • Comparison operators: =, <>, <, >, <=, >=
  • Logical operators: And, Or, Not
• Control structures: Control the flow of execution
  • Conditional statements:
    • If...Then...Else: Executes code blocks based on a condition
    • Select Case: Executes code blocks based on a variable's value
  • Looping statements:
    • For...Next: Executes a code block a specified number of times
    • Do...Loop: Executes a code block until a condition is met
    • While...End While: Executes a code block while a condition is true
    • For Each...Next: Iterates over the elements in a collection or array
• Procedures: Code blocks that perform specific tasks
  • Subroutines: Procedures that do not return a value
  • Functions: Procedures that return a value
  • Procedure declaration:
    • Sub procedureName(parameterList)
    • Function functionName(parameterList) As DataType
  • Calling procedures:
    • Call procedureName(argumentList)
    • variable = functionName(argumentList)
• Modules: Procedure and variable containers
• Code is organized into reusable and manageable blocks

Database Integration

• VB applications can interact with databases to manipulate, retrieve, and store data
• ADO.NET is the primary technology for database access in VB.NET
• Ado.NET provides objects for connecting to databases, executing commands, and retrieving data
• Common ADO.NET objects:
  • Connection: Represents a connection to a database
  • Command: Represents a SQL command or stored procedure
  • DataAdapter: Retrieves data and populates a DataSet from a database
  • DataSet: An in-memory cache of data
  • DataReader: Provides fast, forward-only access to data
• Steps for database integration:
  • Establish a connection to the database
  • Create a Command object with a SQL query or stored procedure
  • Execute the command and retrieve the data
  • Populate a DataSet or DataReader with the results
  • Display or manipulate the data in the application
• SQL is used to interact with databases
• Common SQL statements:
  • SELECT: Retrieves data from a table
  • INSERT: Adds new data to a table
  • UPDATE: Modifies existing data in a table
  • DELETE: Removes data from a table
• Data binding: Connects UI controls to data sources
• Data can be displayed and updated automatically
• DataGridView control: Displays tabular data
• A DataGridView control can be bound to a DataSet or DataReader to display data from a database
• Parameterized queries:
  • Parameters in SQL queries prevent SQL injection attacks
  • Improves security and performance
• Transactions:
  • Operations are treated as a single unit of work
  • Ensures data consistency and integrity
  • If any operation fails, the entire transaction is rolled back