Lambda expression syntax in C Sharp (C#) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a lambda expression in C#?

A lambda expression is a short way to write anonymous functions using the syntax (input) => expression or (input) => { statements }. It is often used for inline code like in LINQ queries or event handlers.

beginner

How do you write a lambda expression that takes one integer and returns its square?

You write it as: x => x * x. Here, x is the input parameter, and x * x is the expression returned.

intermediate

What is the difference between a lambda expression with an expression body and one with a statement body?

An expression body lambda returns the result of a single expression directly, like x => x + 1. A statement body lambda uses braces and can have multiple statements, like x => { int y = x + 1; return y; }.

beginner

Can a lambda expression have multiple parameters? Show an example.

Yes, a lambda can have multiple parameters separated by commas. Example: (x, y) => x + y adds two numbers.

intermediate

How do you specify the type of parameters in a lambda expression?

You can specify types explicitly like (int x, int y) => x + y, but usually the compiler infers the types from context.

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

A x => x * 2

B (int x) => x * 2

C x => { return x * 2; }

D => x * 2

Option A is correct. Option B is valid syntax but not the best choice here since the question implies invalidity; Option C is missing a semicolon after return, which is corrected here. Option D is missing the parameter.

What does the lambda expression (x, y) => x - y do?

A Divides x by y

B Adds x and y

C Multiplies x and y

D Subtracts y from x

The expression subtracts y from x.

How do you write a lambda expression with no parameters that returns 42?

A => 42

B x => 42

C () => 42

D (x) => 42

Option C correctly shows a lambda with no parameters returning 42.

Which syntax is used for a statement body lambda?

A (x) => { return x + 1; }

B x => { x + 1 }

C x => x + 1

D x => return x + 1

Option A uses braces and a return statement, which is the statement body syntax.

Can the compiler infer parameter types in lambda expressions?

A Yes, always

B Yes, if context provides type information

C Only for single parameter lambdas

D No, never

The compiler infers types when it can, based on the context where the lambda is used.

Explain the basic syntax of a lambda expression in C# and give an example.

Think about how you write a small function without a name.

Describe the difference between expression body and statement body lambdas with examples.

One is short and simple, the other can do more steps.