gistfile1.cs

private static void Test()
{
    var sw = new Stopwatch();
    sw.Start();

    for (int i = 0; i < 1000; i++)
    {
        var count = GetPalindromic(10000000000000000000);
    }
            
    var elapsed = sw.ElapsedMilliseconds;
    Console.WriteLine("Elapsed: {0}ms", elapsed);   // Elapsed: 5 ms
}

private static int GetPalindromic(UInt64 number)
{
    var count = 0;

    for (UInt64 i = 10; i <= number; i*= 10)
    {
        var l = i.ToString().Length;
        var f = Math.Floor(l/2.0);
        count += (int)(0.9 * Math.Pow(10, f));
    }

    return count;
}