- 01Setting up (what you'll need)
- 02Your first output (Console.WriteLine)
- 03Using variables
- 04Branching (the If statement)
- 05Repeating (the For statement)
- 06Writing a function (a procedure)
- 07Working with arrays
- 08Repeating (the While statement)
- 09Working with classes (object orientation)
- 10Error handling (Try...Catch)
- 11Sorting an array
- 12Recursive functions
- 13Using the standard library
- 14The Select Case statement
- 15Conditional expressions (the If operator)
- 16Inheritance (extending a class)
- 17Writing comments
- 18Logical operators (AndAlso, OrElse, Not)
- 19Constants (Const)
- 20Splitting and joining strings (Split and Join)
- 21Writing null-safe code (the If operator)
- 22Searching an array (Array.IndexOf)
- 23Transforming an array (map)
- 24Two-dimensional arrays (tabular data)
- 25Creating your own exception class
- 26Default arguments (Optional parameters)
- 27Working with HashSet (sets)
- 28Checking correctness with Debug.Assert (a first step towards testing)
- 29Higher-order functions (passing a function as an argument)
- 30Stacks and queues (the basics of data structures)
- 31The basics of type conversion (casting)
- 32An introduction to regular expressions (pattern matching)
- 33The binary search algorithm
- 34Building a Caesar cipher (a letter-shifting cipher)
- 35Understanding how bubble sort works
- 36Assembling and displaying a date
- 37Writing several tests together (multiple test cases)
- 38Speeding up calculation with memoization (caching)
- 39Normalizing strings (Trim and case)
- 40Shallow copies versus deep copies
- 41The basics of enums
- 42Flattening a list
- 43Reversing a string and testing for a palindrome
- 44Pairing up two arrays (the zip operation)
- 45Rounding numbers (Floor, Ceiling, Round)
- 46Multi-line text (building it with vbCrLf)
- 47Returning several values from a function (tuples)
- 48Finding the GCD and LCM (the Euclidean algorithm)
- 49Formatting numbers (aligning digits and decimal places)
- 50Cleaning up with Try / Catch / Finally
- 51Writing general functions with generics
- 52The basics of reading and writing files
- 53Generating random numbers
- 54Bitwise operations (And, Or, Xor, shifts)
- 55Receiving command-line arguments
- 56Pausing for a set time (Thread.Sleep)
- 57Watch out for floating-point error
- 58Reading a value from standard input
- 59FizzBuzz (the classic exercise)
- 60Testing whether a number is prime
- 61Set operations with HashSet (union, intersection, difference)
- 62Converting between bases (binary and hexadecimal)
- 63Checking that brackets match (an application of stacks)
- 64Testing whether two words are anagrams
- 65Testing whether a year is a leap year
- 66Converting temperatures (Celsius and Fahrenheit)
- 67Finding the prime factors
- 68[Project] Build a simple inventory system
Working with HashSet (sets)
This lesson covers handling data without duplicates using VB.NET's HashSet, with the aim of understanding the set as a data structure.
HashSet(Of T) represents a set that holds no duplicates. Unlike an array or a list, adding the same value again collapses into one, and membership checks are fast.
The sample code builds a HashSet from the duplicate-laden array {1, 2, 2, 3, 3, 3} with New HashSet(Of Integer)(nums), and uniqueNums is left holding just 1, 2, and 3. Note Contains() checking whether a value is present.
A common early stumble is that a HashSet's ordering is not guaranteed. It will not necessarily be in insertion order as an array or list is, so where order matters a list suits better.
In professional work, HashSet is used wherever "one of each is enough" — a tag list, checking user IDs for duplicates.
๐งช This site can't compile or run VB.NET directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser โ nothing is sent anywhere).