Question

I’m getting ‘Sequence contains no elements’ with LINQ FirstOrDefault.

int? locationId = _ctx.m_locations.FirstOrDefault(
                       l => l.name.ToLower() == countyOrTown.ToLower()
                  ).location_key;

I thought the whole point of FirstOrDefault is that it doesn’t raise an exception if there are no entries in the database and just returns null?

Answer 1

Since as you say yourself, .FirstOrDefault() will return a NULL value, you need to first check for that NULL and only if it’s NOT NULL then access it’s .location_key property:

int? locationId = null;

var firstOrDefault = _ctx.m_locations.FirstOrDefault(l => l.name.ToLower() == countyOrTown.ToLower());

if(firstOrDefault != null)
    locationId = firstOrDefault.location_key;