Initial data commit

Task/Five-weekends/C-sharp/five-weekends-2.cs

@@ -0,0 +1,37 @@
+using System;
+using System.Linq;
+using System.Collections.Generic;
+
+public class Program
+{
+    public static void Main()
+    {
+        const int startYear = 1900, endYear = 2100;
+
+        var query = (
+            from year in startYear.To(endYear)
+            from month in 1.To(12)
+            where DateTime.DaysInMonth(year, month) == 31
+            select new DateTime(year, month, 1) into date
+            where date.DayOfWeek == DayOfWeek.Friday
+            select date)
+            .ToList();
+
+        Console.WriteLine("Count: " + query.Count);
+        Console.WriteLine();
+        Console.WriteLine("First and last 5:");
+        for (int i = 0; i < 5; i++)
+            Console.WriteLine(query[i].ToString("MMMM yyyy"));
+        Console.WriteLine("...");
+        for (int i = query.Count - 5; i < query.Count; i++)
+            Console.WriteLine(query[i].ToString("MMMM yyyy"));
+        Console.WriteLine();
+        Console.WriteLine("Years without 5 weekends:");
+        Console.WriteLine(string.Join(" ", startYear.To(endYear).Except(query.Select(dt => dt.Year))));
+    }
+}
+
+public static class IntExtensions
+{
+    public static IEnumerable<int> To(this int start, int end) => Enumerable.Range(start, end - start + 1);
+}