FirstOrDefault returns NullReferenceException if no match is found

Question

Here is my code:

string displayName = Dictionary.FirstOrDefault(x => x.Value.ID == long.Parse(options.ID)).Value.DisplayName;

The code works

Answer 1

That is because FirstOrDefaultcan return null causing your following .Value to cause the exception. You need to change it to something like:

var myThing = things.FirstOrDefault(t => t.Id == idToFind);

if(myThing == null)
    return; // we failed to find what we wanted
var displayName = myThing.DisplayName;