FirstOrDefault: Default value other than null

Question

As I understand it, in Linq the method FirstOrDefault() can return a Default value of something other than null. What I haven\'t worked out is wha

Answer 1

Actually, I use two approaches to avoid NullReferenceException when I'm working with collections:

public class Foo
{
    public string Bar{get; set;}
}
void Main()
{
    var list = new List();
    //before C# 6.0
    string barCSharp5 = list.DefaultIfEmpty(new Foo()).FirstOrDefault().Bar;
    //C# 6.0 or later
    var barCSharp6 = list.FirstOrDefault()?.Bar;
}

For C# 6.0 or later:

Use ?. or ?[ to test if is null before perform a member access Null-conditional Operators documentation

Example: var barCSharp6 = list.FirstOrDefault()?.Bar;

C# older version:

Use DefaultIfEmpty() to retrieve a default value if the sequence is empty.MSDN Documentation

Example: string barCSharp5 = list.DefaultIfEmpty(new Foo()).FirstOrDefault().Bar;