C # 6 null conditional statement operator for .Any ()?

Question

In the example given here ( and on other other sites ) in relation to the operator with a null condition, he claims that

int? first = customers?[0].Orders.Count(); 

can be used to get an invoice for the first customer. But this statement does not check for clients in the collection and may cause exclusion from a range out of range. What should be the correct (preferably one-line) operator that takes care of checking for the existence of elements?

Answer 1

The null condition statement is for conditional accessnull , but this is not the problem you are facing.

. null FirstOrDefault :

int? first = customers.FirstOrDefault()?.Orders.Count(); 

, , , FirstOrDefault null, .

: w.b, , , ElementAtOrDefault FirstOrDefault

Answer 2

LINQ DefaultIfEmpty, IEnumerable , :

int? first = customers?.DefaultIfEmpty().First().Orders.Count();

:

int? first = customers?.DefaultIfEmpty().ToArray()[0].Orders.Count();

Answer 3

, , ( ) IndexOutOfRangeException s. :

myArray?.Length > 42 ? myArray[42] : null

@w.b. , ElementAtOrDefault:

myArray?.ElementAtOrDefault(42) 

NullReferenceException, IndexOutOfRangeException.