var numbers = new[] {1,2,3,4,5};

var allNumbersAreOdd = numbers.All(n => (n & 1) == 1);
Console.WriteLine(allNumbersAreOdd); //False

var allNumbersArePositive = numbers.All(n => n > 0);
Console.WriteLine(allNumbersArePositive); //True

Note that the All method functions by checking for the first element to evaluate as false according to the predicate. Therefore, the method will return true for any predicate in the case that the set is empty:

var numbers = new int[0];
var allNumbersArePositive = numbers.All(n => n > 0);
Console.WriteLine(allNumbersArePositive); //True