Or you could use SymmetricExceptWith

Modifies the current HashSet object to contain only elements that are present either in that object or in the specified collection, but not both.

var h1 = new HashSet<int>() { 1, 2, 3, 4, 5 }; var h2 = new HashSet<int>() { 4, 5, 6, 7, 8 }; h1.SymmetricExceptWith(h2); Console.WriteLine(string.Join(",", h1)); 

Output

1,2,3,7,6,8 

Internally its just uses

foreach (T item in other) { if (!Remove(item)) { AddIfNotPresent(item); } } 

Source Code here

Or you could use SymmetricExceptWith

Modifies the current HashSet<T> object to contain only elements that are present either in that object or in the specified collection, but not both.

var h1 = new HashSet<int>() { 1, 2, 3, 4, 5 }; var h2 = new HashSet<int>() { 4, 5, 6, 7, 8 }; h1.SymmetricExceptWith(h2); Console.WriteLine(string.Join(",", h1)); 

Output

1,2,3,7,6,8 

Internally it just uses

foreach (T item in other) { if (!Remove(item)) { AddIfNotPresent(item); } } 

Source Code here