LINQ Interview Question #40

What does First do in LINQ?

Filtering, Projection, Ordering & Element Operators Junior Beginner

Quick Interview Answer

First returns the first element of a sequence. An overload can return the first element satisfying a predicate.

Detailed Explanation

First returns the first element of a sequence. An overload can return the first element satisfying a predicate.

If no matching element exists, First throws InvalidOperationException. Use it when the application expects an element to exist and absence represents an exceptional or invalid state.

Code Example

var firstProduct = products.First();

var firstActive =
    products.First(p => p.IsActive);