Property patterns in C Sharp (C#) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a property pattern in C#?

A property pattern lets you check if an object has certain properties with specific values or conditions, making it easier to match complex data shapes in a clear way.

beginner

How do you write a simple property pattern to check if a Point object has X equal to 0?

You write: point is { X: 0 }. This means the object 'point' has a property 'X' with value 0.

intermediate

Can property patterns check nested properties? Give an example.

Yes. For example: person is { Address: { City: "Paris" } } checks if 'person' has an 'Address' property whose 'City' is "Paris".

intermediate

What happens if a property in a property pattern is null or missing?

The pattern does not match. Property patterns require the property to exist and meet the condition; otherwise, the match fails.

intermediate

How can you combine multiple property patterns in one check?

You can list multiple properties inside braces, like obj is { Prop1: 5, Prop2: "hello" }, which means both conditions must be true.

What does the pattern obj is { Name: "Alice" } check?

A If obj has any property named Name

B If obj is a string "Alice"

C If obj is null

D If obj has a property Name equal to "Alice"

The pattern checks if the object has a property called Name with the value "Alice".

Can property patterns be used to check nested properties?

A Only for properties of type int

B No, only top-level properties

C Yes, by nesting braces for each property level

D Only if the object is a struct

Property patterns support nested properties by using nested braces, like { Address: { City: "Paris" } }.

What happens if a property in the pattern is missing on the object?

A The pattern does not match

B The pattern matches anyway

C The pattern throws an exception

D The property is ignored

If the property is missing, the pattern does not match because the condition cannot be verified.

How do you check multiple properties in one property pattern?

A List properties separated by commas inside braces

B Use multiple 'is' keywords

C Use && operator between patterns

D Use a switch statement

You list multiple properties inside one set of braces separated by commas, like { Prop1: 1, Prop2: 2 }.

Which C# version introduced property patterns?

A C# 6

B C# 9

C C# 8

D C# 7

Property patterns were introduced in C# 9 to improve pattern matching capabilities.

Explain what a property pattern is and how it helps in checking object properties.

Think about how you check if an object has certain values inside it.

Describe how to write a property pattern that checks multiple properties and nested properties.

Imagine checking a person's address city inside the person object.