LINQ Interview Question #74

What does Contains do in LINQ?

Joins, Grouping, Set & Quantifier Operators Mid-Level Intermediate

Quick Interview Answer

Contains determines whether a sequence contains a specified value according to its equality semantics. It is useful for membership checks.

Detailed Explanation

Contains determines whether a sequence contains a specified value according to its equality semantics. It is useful for membership checks.

With EF Core, a local collection Contains call inside a query is commonly translated to an SQL IN-style condition when the provider supports it.

Code Example

var allowedIds = new[] { 2, 5, 8 };

bool containsFive = allowedIds.Contains(5);

var products = db.Products
    .Where(p => allowedIds.Contains(p.Id));