GroupBy then Select with conditional record addition

I am having LINQ query in which I have to response with a result set which is depending on inner field collection. I have done the thing via LINQ query then a foreach but I wanted to avoid foreach loop and do it somehow from group by

List<ResultModel> result = new List<ResultModel>();           
var tempResultSet = _context.MainRecordTable.Where(h => h.id)
    .Select(lev => new 
    {
        Contacts = (lev.basetable2 != null 
                            && lev.basetable2.basetable3 != null 
                            && lev.basetable2.basetable3.basetable6 != null
                            &&  lev.basetable2.basetable3.basetable6.Any(h=>h.contact != null)
                            ? lev.basetable2.basetable3.basetable6.Where(h=>h.contact != null).Select(h=>h.contact).Distinct() : null),
        Key1 = lev.basetable5 != null ? lev.basetable5.Id : null,
        Key2 = lev.basetable2 != null && lev.basetable2.basetable3 != null && lev.basetable2.basetable3.basetable4 != null ?
                            lev.basetable2.basetable3.basetable4.id      : null

    })
    .Distinct()
    .ToList();

foreach (var x in tempResultSet)
{
    if (x.Contacts != null)
    {
        foreach (var contact in x.Contacts)
        {
            result.Add(new ResultModel
            {
                Key1 = x.Key1,
                Key2 = x.Key2,                           
                ContactKey = contact.id
            });
        }
    }
    else
    {
        result.Add(new ResultModel
        {
            Key1 = x.Key1,
            Key2 = x.Key2                        
        });
    }
}

return result;

>Solution :

You can use SelectMany to flatten the array, e.g.:

List<ResultModel> result = _context.MainRecordTable.Where(h => h.id)
    .Select(lev => new 
    {
        Contacts = (lev.basetable2 != null 
                            && lev.basetable2.basetable3 != null 
                            && lev.basetable2.basetable3.basetable6 != null
                            &&  lev.basetable2.basetable3.basetable6.Any(h=>h.contact != null)
                            ? lev.basetable2.basetable3.basetable6.Where(h=>h.contact != null).Select(h=>h.contact).Distinct() : null),
        Key1 = lev.basetable5 != null ? lev.basetable5.Id : null,
        Key2 = lev.basetable2 != null && lev.basetable2.basetable3 != null && lev.basetable2.basetable3.basetable4 != null ?
                            lev.basetable2.basetable3.basetable4.id      : null

    })
    .Distinct()
    .ToList()
    .SelectMany(x => {
      if (x.Contacts == null)
        return new ResultModel[]  
        {
          Key1 = x.Key1, 
          Key2 = x.Key2,
        };
      else 
        return x.Contacts.Select(contact => new ResultModel() 
          { 
            Key1 = x.Key1, 
            Key2 = x.Key2, 
            ContactKey = contact.id,
          }).ToArray();        
    })
    .ToList();

In the SelectMany, it is checked whether the contact list is set; if not, a single item is returned, otherwise, an item for each contact is returned.