c# - Linq query to consider even records and skip odd record -

below model :

public class mydata {     public int regionid { get; set; }     public string region { get; set; }     public list<test> tests { get; set; } }  public class test {     public int? testid { get; set; }     public list<subtest> subtests { get; set; } } 

below method :

private void mymethod(int testid, int lasttestid) {     var list = new list<mydata>();//contains records     if (testid == 0)     {         var test1 = list[0].tests[0];         var test2 = list[0].tests[1];         var regionids = new list<int>();         int counter = 0;         foreach (var item in list)         {             counter = 0;             foreach (var test in item.tests)             {                 if (test.subtests.count != 0 && counter % 2 != 0)                     regionids.add(item.regionid);                  counter++;             }         }     }     else     {         var test1 = list[0].tests[0];         var regionids = new list<int>();         foreach (var item in list)         {             counter = 0;             foreach (var test in item.tests)             {                 if (test.subtests.count != 0)                     regionids.add(item.regionid);                  counter++;             }         }     } } 

in above method when testid 0 have 2 records in tests , when testid > 0 have 1 record in tests.

now trying find region ids there no subtests(subtest.count=0) test when have 2 test want consider last test , count subtest last test.

my code working fine thing having code duplication want simplify.

instead of loop prefer linq not knowing how linq use loop.

update:

input :

[0] : region = "abc"       regionid = 1       "testlist":         [          {            testid : 100,            subtests  : //contains records          },          {            testid : 101,            subtests  : //contains records          },        ], [1] : region = "pqr",       regionid = 2       "testlist":         [          {            testid : 100,            subtests  : //contains records          },          {            testid : 101,            subtests  : //no records i.e count = 0          },        ], [2] : region = "lmn",       regionid = 3       "testlist":         [          {            testid : 100,            subtests  : //no records i.e count = 0          },          {            testid : 101,            subtests  : //no records i.e count = 0          }        ] 

expected output :

[2,3] 

can please me simplify process??

list<mydata> list;  ... int[] ids = list.where(x => x.tests.last().subtests.count == 0)                 .select(x => x.regionid)                 .toarray(); 

expression in where methods can explained "last test in tests collection doesn't have subtests".

after found requiered tests list regionid select method , save in array.