What is a HashMap?

Part of the Logic & Flow section of Coddy's C# journey — lesson 46 of 66.

In C#, the equivalent of a HashMap is called a Dictionary. A Dictionary is a collection that stores key-value pairs, allowing you to quickly look up values using their associated keys.

Let's understand the basics:

A Dictionary stores data as key-value pairs

// The syntax is Dictionary<KeyType, ValueType>
Dictionary<string, int> ages = new Dictionary<string, int>();

Cheat sheet

A Dictionary stores key-value pairs and allows quick lookups by key:

// Syntax: Dictionary<KeyType, ValueType>
Dictionary<string, int> ages = new Dictionary<string, int>();

Try it yourself

This lesson doesn't include a code challenge.

Test yourself

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All lessons in Logic & Flow

1Multi-dimensional Arrays

2D Arrays Basics Declaring and Initializing 2D Accessing 2D Array Elements Nested Loops with 2D Arrays Jagged Arrays Common Matrix Operations Recap - Multi-dimensional

4Flow Control Techniques

Early Returns Guard Clauses Jump Statements (goto)Break and Continue Flatten Nested Conditionals

7Logical Operators Advanced

Short-Circuit Evaluation Conditional Logical Operators Operator Precedence Recap - Advanced Operators

10HashMap Part 2

HashMap Methods Nested HashMap Recap - Manage Warehouse Recap - HashMap Operations

3Loop Enhancements

Loop Performance Iterating Complex Each Loop Type Refactoring Loops Recap - Optimized Loops

6Null Handling

Null Reference Basics Nullable Value Types Null Checking Patterns Defensive Programming Recap - Null Safety

9HashMap Part 1

What is a HashMap?Declare a HashMap Check If Key Exists Accessing Values Modifying Dictionaries Recap - HashMap

12HashSet Part 2

Math - Union of HashSets Math - Intersection of HashSet Math - Set Difference Math - Symmetric Difference Iterating Over Sets