LINQ "MaxOrDefault"?

How about:

int new_id = 0;

if (C_Movement.list.Any())
    new_id = C_Movement.list.Max(x => x.id) + 1;

DefaultIfEmpty method should help:

int new_id = C_Movement.list.Select(x => x.id).DefaultIfEmpty(-1).Max()+1;

int new_id = C_Movement.list.Max(x => (int?)x.id).GetValueOrDefault(-1) + 1;

where GetValueOrDefault is a method of Nullable<T>.

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