How does LINQ Except work? [duplicate]

Answer 1

The other answers are telling you how you can remove a set of numbers from another set. Reading your question I think you want what's in the first but not in the second, and viceversa:

var numbers1 = new [] { 2.0, 2.1, 2.2, 2.3, 2.4, 2.5 };
var numbers2 = new [] { 2.2, 2.8 };

var intersect = numbers1.Intersect(numbers2);
var diff = numbers1.Concat(numbers2).Except(intersect);

Answer 2

Taken from 101 LINQ Samples:

int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 }; 
int[] numbersB = { 1, 3, 5, 7, 8 }; 

IEnumerable<int> aOnlyNumbers = numbersA.Except(numbersB); 

Console.WriteLine("Numbers in first array but not second array:"); 
foreach (var n in aOnlyNumbers) 
{ 
    Console.WriteLine(n); 
}

Result

Numbers in first array but not second array: 0 2 4 6 9

Answer 3

For example this will not return any result...

That's correct.

2.2 exists in the first collection, so there is nothing to return.

It has nothing to do with the lengths of the arrays.