class Person
{
public string Name {get; set;}
public DateTime BirthDate {get; set:}
}
var persons = new[]
{
new { Name = "Юрий Васильевич Кондратюк", BirthDate = new DateTime(1897, 06, 9) },
new { Name = "Михаил Фёдорович Решетнёв", BirthDate = new DateTime(1924, 11, 10) },
new { Name = "Михаил Тимофеевич Калашников", BirthDate = new DateTime(1919, 11, 10) },
new { Name = "Сергей Павлович Королёв", BirthDate = new DateTime(1907, 1, 12) },
new { Name = "Михаил Васильевич Ломоносов", BirthDate = new DateTime(1711, 11, 8) }
};
int[] arr = persons.Where(n => n.Name.Contains("Михаил"))
.GroupBy(day => day.BirthDate.Day)
.Select(count => count.Count())
.ToArray();
Array.ForEach(arr, Console.WriteLine);