C# Dictionaries Explained for Beginners — Key-Value Pairs

You have a class full of students, and you need one student's score, right now. A list makes you search through the items. A dictionary finds it directly: give it a key, like a name, and it gives you the value, the score. In this lesson, you learn C# dictionaries step by step, and we build a real Student Lookup app in VS Code that shows, looks up, adds, and updates scores, and handles unknown students without crashing. This is episode 16 of the Complete C# Course for Beginners on ITHubCoding. It continues from episode 15, where we learned lists:    • C# Lists Explained for Beginners — Add, Re...   Earlier episodes are in the course playlist. WHAT YOU WILL LEARN • Arrays, lists, and dictionaries: finding a value by its index vs by its key • Key-value pairs: a student's name is the key, the score is the value • Creating a dictionary: Dictionary of string and int, scores = new() • Adding entries with Add, and with square brackets • Add vs square brackets: Add throws for a key that already exists, square brackets add or update • Reading a value by its key, and the KeyNotFoundException for a missing key • The safe way: TryGetValue (true or false, never a crash) • Updating a value: the key stays, only the value changes • ContainsKey: it checks the keys, not the values • Looping through every key-value pair with foreach and KeyValuePair, and Count • Four common mistakes, including expecting a dictionary to be sorted CHAPTERS 0:00 Preview: the student lookup app 0:34 What is a dictionary? (keys and values) 1:11 Create a dictionary (Dictionary of string and int) 2:25 Add entries (Add vs square brackets) 3:18 Read values, KeyNotFoundException, and TryGetValue 4:52 Update values and ContainsKey 6:13 foreach over key-value pairs, and Count 7:00 Build the student lookup app 10:04 Common mistakes (missing key, duplicate Add, keys vs values, order) 11:10 Recap + challenge THE PROGRAM StudentLookup is a menu app: 1 Show all students, 2 Look up a student, 3 Add or update a score, 4 Exit. It starts with Ali (85), Sara (92), and Tom (78). Looking up Zara prints "No student named Zara." instead of crashing, option 3 adds Mia as a new student and updates Tom's score from 78 to 81, and a score that is not a whole number from 0 to 100 changes nothing. YOUR CHALLENGE Create a dictionary of three products and their prices, then look up one product by name with TryGetValue. Test a product that exists, and one that does not. Details are in the pinned comment. SOURCE CODE The full code of this episode, explained step by step, with the challenge solution and automated tests: https://github.com/shuhratrahmonov146... OFFICIAL DOCUMENTATION Dictionary (the Dictionary of TKey and TValue class): https://learn.microsoft.com/dotnet/ap... Dictionary.TryGetValue: https://learn.microsoft.com/dotnet/ap... Dictionary.ContainsKey: https://learn.microsoft.com/dotnet/ap... KeyNotFoundException: https://learn.microsoft.com/dotnet/ap... SortedDictionary: https://learn.microsoft.com/dotnet/ap... NOTES • Recorded with .NET SDK 10.0.113 and VS Code on Linux. The code works the same on Windows and macOS. • The typing and every program run are real, including the KeyNotFoundException crash in chapter 5. Build waits are shown at 2–4× and the live menu runs at 1.5×, always marked on screen with a speed badge. • The four mistakes in chapter 9 are real runs (and one real compiler error) of small experiments made off camera. • The narration uses a computer-generated (neural text-to-speech) voice. The background music is original, made for this video. Share your challenge solution in the comments! #csharp #dotnet #programming