program.cs

// response to http://blog.thesoftwarementor.com/2015/10/20/using-f-to-solve-a-constraints-problem/

public static void Main(string[] args)
{
	var numbers = Enumerable.Range(0, 10000);

	var modFactor = 3;
	var constraints = new Func<int, bool>[]
		{
			i => i.ToString().Length == 4,
			i => i % modFactor == 0,
			i => i > 10 && i.ToString().First() == i.ToString().Last()
		};

	Func<int, bool> isMatch = i => constraints.All(c => c(i));

	foreach (var item in numbers.Where(isMatch))
	{
		Console.WriteLine(item);
	}
}