Pattern matching in switch in C Sharp (C#) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is pattern matching in a switch statement?

Pattern matching in a switch statement lets you check an expression against different patterns, not just fixed values. It helps you test types, properties, or conditions directly in each case.

beginner

How do you match a type in a switch case using pattern matching?

You write the type name followed by a variable name, like case int number:. This matches if the value is an int and assigns it to number.

intermediate

What does the when keyword do in a switch case?

The when keyword adds an extra condition to a case. The case matches only if the pattern matches and the when condition is true.

intermediate

Explain the difference between case int n: and case int n when n > 0:.

case int n: matches any integer and assigns it to n. case int n when n > 0: matches only positive integers because of the when condition.

beginner

Can you use pattern matching in switch expressions as well as statements?

Yes! Pattern matching works in both switch statements and switch expressions, allowing concise and readable code for selecting values based on patterns.

What does case string s: do in a switch statement?

A Matches any string and assigns it to s

B Matches only empty strings

C Matches any integer and assigns it to s

D Matches null values only

The case matches any value of type string and assigns it to the variable s.

Which keyword adds an extra condition to a switch case pattern?

A if

B where

C when

D case

The 'when' keyword adds a condition that must be true for the case to match.

What happens if no pattern matches in a switch statement with pattern matching?

A The switch statement is skipped

B The program crashes

C The first case runs anyway

D The default case runs if provided

If no pattern matches, the default case runs if it exists; otherwise, no case runs.

Which of these is a valid pattern matching case in C#?

A case n int:

B case int n when n < 10:

C case (int) n:

D case int:

Option B correctly uses type matching with a variable and a when condition.

Can pattern matching in switch check properties of an object?

A Yes, using property patterns

B Only with loops

C Only with if statements

D No, only types

Pattern matching supports property patterns to check object properties inside switch cases.

Describe how pattern matching improves switch statements in C#.

Think about how you can check more than just fixed values.

Explain how to use the 'when' keyword in a switch case with an example.

It adds extra conditions to cases.