LINQ statement optimization

Question

var person = People.SingleOrDefault(p => p.Name == parameter);
SelectedPerson = person ?? DefaultPerson

Could this be written in one statement? Measing can I provide the default element that SingleOrDefault returns?

I am looking for someting like this (the second argument is the default element I provide).

var person = People.SingleOrDefault(p => p.Name == parameter, DefaultPerson);

The solution should also work for value types (ints, doubles, enums, structs, ...).

Answer 1

You can use DefaultIfEmpty():

var person = People.Where(p => p.Name == parameter).DefaultIfEmpty(DefaultPerson).Single();

Answer 2

You can define an extension:

public static T SingleOrDefault<T>
    (this IEnumerable<T> list, T defaultValue) 
    where T : class
{
    return list.SingleOrDefault() ?? defaultValue;
}

and then call it with:

var person = People.SingleOrDefault(p => p.Name == parameter, DefaultPerson);