4: Using Methods and Exceptions 367 in .NET

Draw GS1 - 12 in .NET 4: Using Methods and Exceptions 367

The Basics of Making Methods367 A Simple Example368 Methods that Return Values 369 Declaring the method s return type370 Using the return statement to return the value370 Using Methods that Take Parameters 371 Declaring parameters 371 Understanding pass-by-value372

Understanding Exceptions373 Catching Exceptions 374 Catching Different Exception Types 375 Using the Exception Message 376 Using a finally Block376

What Is Object-Oriented Programming 377 Understanding Objects379 Objects have identity379 Objects have type380 Objects have state381 Objects have behavior381 The Life Cycle of an Object 382 Working with Related Classes383 Inheritance 383 Interfaces384 Declaring a Class 385 Picking class names 385 What goes in the class body 385 Using Fields386 Creating Properties387 Using Methods389 Creating Constructors 390 Basic constructors 391 Default constructors 392 Using this392 Working with Static Members393 Working with static fields or properties394 Using static methods 394

Understanding Inheritance 397 A real-world explanation 398 A fun explanation 399 A business-world explanation399 Inheritance hierarchies400 Creating Derived Classes 400 Overriding Methods401 Protecting Your Members 402 Using this and base in Your Derived Classes403 Inheritance and Constructors 404 Casting Up and Down 405 Determining an Object s Type: The is Operator 406 Poly What 407

Looking at Classes, Structures, and Modules411 Working with Source Files412 Creating Sub Procedures413 Working with Statements 414 Creating Identifiers 415 Adding Comments to Your Code416 Declaring Variables 416 Working with Data Types 417 Integer types 418 Floating-point types 419 The decimal type419 The char type420 The Boolean type 420 Working with Strings420 Declaring and initializing strings420 Combining strings 421 Converting strings421 Working with Arithmetic Operators 422 Combining Operators 423 Using Assignment Statements 424 Using Assignment Operators425

Using If Statements 427 The basic If statement 428 The single-line If429 The Else clause 429 Nesting If statements 430 The ElseIf structure430 Using Conditional Expressions433 Getting Logical434 Using the Not operator 435 Working with the And operator 435 Utilizing the AndAlso operator 435 Using the Or and OrElse operators436 Using the Select Case Statement 436 Working with For/Next Loops438 Using While loops439 Utilizing Do loops 440 Exiting a loop 441 Nesting your loops 441

Using Sub Procedures444 Working with Functions445 Getting Finicky about Parameters446 Understanding Exceptions448 Catching exceptions448 Using a Finally block 450 Using Arrays 450 Creating an array 451 Initializing an array451 Using For loops with arrays 452 Using two-dimensional arrays 452

Introducing Object-Oriented Programming 455 Objects have identity456 Objects have type456 Objects have state456 Objects have behavior457 Creating Objects from Classes 458 Declaring Classes 458 Using fields 459 Creating properties 460 Using methods 462 Creating constructors463 Using Shared Members464

Understanding Inheritance 467 Understanding Inheritance Hierarchies 469 Creating a Derived Class 469 Overriding Methods470 Using Protected Members471 Using the MyBase Keyword 472 Using Casting with Inheritance472 Determining an Object s Type 474 Confronting Polymorphism 474

Understanding the Basics of Relational Databases 480 Gathering data into tables480 Organizing with rows and columns481

Distinguishing data with primary keys and foreign keys 481 Indexing your data for fast retrieval 484 Working with Databases Using SQL 485 Creating a table with CREATE TABLE486 Deleting a table with DROP TABLE489 Getting data with SELECT490 Selecting only specific rows with the WHERE clause 491 Adding data with INSERT 491 Modifying data with UPDATE 492 Removing data with DELETE 493 Piecing Together SQL Statements 494 Connecting to Data with ADONET 495 Issuing Database Commands498 Calling statements that return no data498 Calling a stored procedure499 Calling statements that return one data item500 Displaying Data on a Web Page 501 Retrieving Data from a Table 503 Adding Security to Your SQL Statements Read This!504

Writing Data to a Page with a Label 507 Binding to Data 509 Creating a data source 509 Using a data source 516 Repeating Through a Result Set 518 Setting server control properties in a Repeater control 519 Adding some style to the Repeater control 520 Altering the look of the Repeater control s rows 521 Creating a Data-Entry Page 523