how to write this into linq to object query?

Question

from a list, which got 3 attributes I want to return a new list of that class where attribut1 recurrence in the list equals X

for an example this;

1,a,b
1,c,d
1,e,f
2,a,b
2,c,d
3,a,b
3,c,d
3,e,f
4,a,b
5,a,b
5,c,d
5,e,f
6,a,b
6,e,f

where X = 1 would return that list

4,a,b

where X = 2 would return that list

2,a,b
2,c,d
6,a,b
6,e,f

where X = 3 would return that list

1,a,b
1,c,d
1,e,f
3,a,b
3,c,d
3,e,f
5,a,b
5,c,d
5,e,f

Answer 1

Perfect case for grouping!

var groups = list.GroupBy(s => s.Attribute1);
var recur_1 = groups.Where(g => g.Count() == 1).SelectMany(s => s);
var recur_2 = groups.Where(g => g.Count() == 2).SelectMany(s => s);
var recur_3 = groups.Where(g => g.Count() == 3).SelectMany(s => s);