LINQ Interview Question #41

What does FirstOrDefault do?

Filtering, Projection, Ordering & Element Operators Mid-Level Intermediate

Quick Interview Answer

FirstOrDefault returns the first element, or the default value when the sequence contains no matching element. For reference types the default is normally null; for non-nullable value types it is the type's default value.

Detailed Explanation

The caller should handle the possibility that no element was found. In nullable-aware C# code, this is especially important for reference types.

Code Example

var product = products
    .FirstOrDefault(p => p.Id == id);

if (product is null)
{
    return NotFound();
}