c# - How can I get all subsets of a set that respect the order -

i'm looking c# example give me subsets of set while respecting order.

for example have a,b , like:

a b ab ba 

please note purpose ab != ba.

the solution should generic input type:

list<list<t>> getsubsets<t>(list<t> originalset) 

i've come across great solutions using bitwise manipulation ab == ba (e.g generate combinations list of strings) far have failed find solve described above.

any tips/pointers appreciated!

getpermutations() ref. https://stackoverflow.com/a/10630026/1287352

public static list<list<t>> permutationof<t>(hashset<t> set) {     var result = new list<list<t>>();     (var length = 1; length <= set.count; length++)     {         result.addrange(getpermutations<t>(set, length).select(i => i.tolist()));     }     return result; }  private static ienumerable<ienumerable<t>> getpermutations<t>(ienumerable<t> list, int length) {     if (length == 1) return list.select(t => new t[] { t });      return getpermutations(list, length - 1)         .selectmany(t => list.where(e => !t.contains(e)),         (t1, t2) => t1.concat(new t[] { t2 })); } 

usage:

permutationof(new hashset<guid>() { guid.newguid(), guid.newguid(), guid.newguid() }) permutationof(new hashset<string>() { "a", "b", "c" }) 

result:

a b c a, b a, c b, b, c c, c, b a, b, c a, c, b b, a, c b, c, c, a, b c, b,