Recursive pattern matching in C Sharp (C#) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is recursive pattern matching in C#?

Recursive pattern matching allows you to match nested data structures by checking patterns inside patterns, making it easy to work with complex objects step-by-step.

beginner

How does recursive pattern matching differ from simple pattern matching?

Simple pattern matching checks one level of an object, while recursive pattern matching checks inside nested objects or properties, going deeper into the structure.

intermediate

Explain the syntax of recursive pattern matching with an example.

You use nested patterns inside parentheses. For example: <br>

obj is Point { X: 0, Y: 0 }

matches a Point with X and Y properties. You can nest patterns like:<br>

obj is Node { Left: null, Right: Node { Value: 5 } }

to check inside nested objects.

beginner

What C# version introduced recursive pattern matching?

Recursive pattern matching was introduced in C# 8.0, allowing more expressive and readable code when working with nested data.

beginner

Why is recursive pattern matching useful in real-world programming?

It helps to easily check and extract data from complex nested objects like trees or JSON-like structures without writing many if-else statements.

Which C# feature allows checking nested object properties in a single pattern?

A Recursive pattern matching

B Simple if statements

C Loops

D Switch expressions without patterns

Recursive pattern matching lets you check nested properties inside objects in one pattern.

In C#, what keyword is used to test if an object matches a pattern?

A match

B is

C case

D check

The 'is' keyword is used to check if an object matches a pattern.

Which C# version first supported recursive pattern matching?

A C# 9.0

B C# 7.0

C C# 8.0

D C# 6.0

Recursive pattern matching was introduced in C# 8.0.

What does this pattern check? <br>obj is Point { X: 0, Y: 0 }

A If obj is null

B If obj is a string

C If obj has any X and Y values

D If obj is a Point with X and Y equal to 0

This pattern matches a Point object where both X and Y properties are 0.

Why use recursive pattern matching instead of nested if statements?

A It makes code shorter and clearer

B It runs slower

C It is harder to read

D It requires more code

Recursive pattern matching simplifies code by reducing nested if statements and improving readability.

Describe how recursive pattern matching works in C# and give a simple example.

Think about matching an object inside another object.

Explain why recursive pattern matching is helpful when working with complex data structures.

Consider how you would check a tree or JSON data.