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

Recall & Review

beginner

What is a relational pattern in C#?

A relational pattern in C# is a way to compare a value against a condition using relational operators like <, <=, >, >= inside a pattern matching expression.

beginner

Which relational operators can be used in C# relational patterns?

You can use <, <=, >, and >= operators in relational patterns to check if a value is less than, less than or equal to, greater than, or greater than or equal to another value.

intermediate

How do relational patterns improve code readability?

Relational patterns let you write conditions directly inside switch or if statements in a clear and concise way, avoiding extra variables or complex if-else chains.

beginner

Example: What does this C# code do? <br>

case >= 90: Console.WriteLine("Excellent"); break;

This case matches when the value is greater than or equal to 90 and prints "Excellent". It uses a relational pattern to check the value directly.

intermediate

Can relational patterns be combined with other patterns in C#?

Yes, relational patterns can be combined with logical patterns like 'and', 'or', and 'not' to create complex matching conditions.

Which of these is a valid relational pattern in C#?

A case > 10:

B case == 10:

C case != 10:

D case === 10:

Relational patterns use operators like >, <, >=, <=. Equality (==) is a constant pattern, not a relational pattern. '===' is not valid in C#.

What will this code print if value = 75?<br>

switch(value) { case >= 90: Console.WriteLine("A"); break; case >= 70: Console.WriteLine("B"); break; default: Console.WriteLine("C"); }

A A

B B

C C

D No output

75 is not >= 90, so first case fails. 75 is >= 70, so it prints "B".

Can you use relational patterns inside an if statement in C#?

A Yes, but only with variables.

B No, only in switch statements.

C Yes, using the 'is' keyword.

D No, relational patterns are not supported.

Relational patterns can be used with 'is' in if statements, like 'if (x is > 10)'.

Which C# version introduced relational patterns?

A C# 7.0

B C# 8.0

C C# 10.0

D C# 9.0

Relational patterns were introduced in C# 9.0.

What does this pattern mean? 'case < 0:'

A Matches values less than zero.

B Matches values equal to zero.

C Matches values greater than zero.

D Matches all values.

The pattern matches any value less than zero.

Explain what relational patterns are and how they are used in C#.

Think about how you compare numbers in conditions.

Describe how relational patterns can be combined with logical patterns in C#.

Consider how you join multiple conditions in if statements.