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

Recall & Review

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What is a constant pattern in C#?

A constant pattern checks if a value matches a specific constant value. It is used in pattern matching to compare values directly.

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How do you write a constant pattern in a C# switch expression?

You write the constant value directly before the =>, like 5 => "five", or "hello" => "hello",.

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What happens if a constant pattern does not match the value?

The pattern matching moves on to the next pattern or the default case if no match is found.

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Can constant patterns be used with is expressions in C#?

Yes, you can use constant patterns with is to check if a variable equals a constant, like if (x is 10).

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Example: What will this code print?<br>

int x = 3;<br>string result = x switch {<br>  1 => "One",<br>  2 => "Two",<br>  3 => "Three",<br>  _ => "Other"<br>};<br>Console.WriteLine(result);

It will print Three because the value 3 matches the constant pattern 3 in the switch expression.

What does a constant pattern do in C#?

A Checks if a value equals a specific constant

B Declares a constant variable

C Creates a new object

D Loops through a collection

A constant pattern compares a value to a fixed constant to check for equality.

Which keyword is used with constant patterns in C# to test a value?

A new

B is

C var

D for

The 'is' keyword is used with constant patterns to check if a value matches a constant.

In a switch statement, how do you write a constant pattern for the number 10?

A case x == 10:

B case const 10:

C case 10:

D case (10):

You write 'case 10:' to match the constant value 10.

What will happen if no constant pattern matches in a switch expression?

A The default case runs if provided

B The program crashes

C The first case runs anyway

D The switch is ignored

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

Can constant patterns be used with strings in C#?

A Only in loops

B No, only numbers

C Only with variables

D Yes, strings can be constant patterns

Constant patterns can match string values directly.

Explain what a constant pattern is and how it is used in C# pattern matching.

Think about how you check if a value equals a fixed number or text.

Describe how a switch expression uses constant patterns to decide which code to run.

Imagine choosing an option based on exact matches.