Expression-bodied lambdas in C Sharp (C#) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an expression-bodied lambda in C#?

An expression-bodied lambda is a concise way to write a lambda expression using a single expression without braces and return keyword. It returns the value of that expression directly.

beginner

How do you write a simple expression-bodied lambda that adds two integers a and b?

You write it as: (a, b) => a + b;

intermediate

What is the difference between a statement-bodied lambda and an expression-bodied lambda?

A statement-bodied lambda uses braces and can have multiple statements, requiring a return keyword if it returns a value. An expression-bodied lambda has no braces and returns the result of a single expression directly.

intermediate

Can expression-bodied lambdas be used with void-returning methods?

Yes, expression-bodied lambdas can be used with void-returning methods if the expression is a statement like a method call. For example: x => Console.WriteLine(x);

beginner

Why are expression-bodied lambdas useful?

They make code shorter and easier to read when the lambda only needs to return the result of a simple expression.

Which of the following is a valid expression-bodied lambda in C#?

A (x, y) => x * y

B (x, y) => { return x * y; }

C (x, y) => { x * y; }

D (x, y) => return x * y;

Option A is an expression-bodied lambda with a single expression. Option B is a statement-bodied lambda. Option C is invalid because it lacks return. Option D is invalid syntax.

What does this expression-bodied lambda do? x => x + 1

A Returns x minus 1

B Returns x plus 1

C Prints x plus 1

D Does nothing

The lambda takes x and returns x plus 1.

Can expression-bodied lambdas contain multiple statements?

A Yes, always

B Only if inside braces

C Yes, if separated by semicolons

D No, only one expression

Expression-bodied lambdas can only have one expression. Multiple statements require braces and become statement-bodied lambdas.

Which keyword is NOT needed in an expression-bodied lambda?

A return

B =>

C lambda parameters

D expression

Expression-bodied lambdas return the expression value implicitly, so 'return' is not used.

How would you write a void expression-bodied lambda that prints a message?

A x => return Console.WriteLine(x)

B x => { Console.WriteLine(x); }

C x => Console.WriteLine(x)

D x => Console.WriteLine(x); return;

Option C is a valid void expression-bodied lambda. Option B is statement-bodied. Options A and D are invalid syntax.

Explain what an expression-bodied lambda is and how it differs from a statement-bodied lambda.

Think about how many statements each can have and how they return values.

Write an example of an expression-bodied lambda that takes two numbers and returns their product.

Use => with a simple multiplication expression.