using System;

using System.Text;

using System.Diagnostics;

using System.Globalization;

​

public class Program {

    public static void Main(string[] args) {

        var tempo = new Stopwatch();

        var data = "10102010";

        var hora = "1010";

        tempo.Start();

        for (var i = 0; i < 10000; i++) {

            var strBuilder = new StringBuilder();

            strBuilder.Append(data).Insert(2, "/").Insert(5, "/");

            strBuilder.Append(" " + hora).Insert(13, ":");

            DateTime dateTime = new DateTime();

            dateTime = Convert.ToDateTime(strBuilder.ToString());

        }

        tempo.Stop();

        Console.WriteLine("SB = {0}ms", tempo.ElapsedMilliseconds);

        tempo.Restart();

        for (var i = 0; i < 10000; i++) {

            var dateTime = Convert.ToDateTime(data.Substring(0, 2) + "/" +

                data.Substring(2, 2) + "/" +

                data.Substring(4, 4) + " " +

                hora.Substring(0, 2) + ":" +

                hora.Substring(2, 2));

        }

        tempo.Stop();

        Console.WriteLine("Concat = {0}ms", tempo.ElapsedMilliseconds);

        tempo.Restart();

        for (var i = 0; i < 10000; i++) {

            var dateTime = DateTime.ParseExact(data+hora, "ddMMyyyyHHmm", CultureInfo.InvariantCulture);

        }

        tempo.Stop();

        Console.WriteLine("ParseExact = {0}ms", tempo.ElapsedMilliseconds);

        tempo.Restart();

        for (var i = 0; i < 10000; i++) {

            var dateTime = new DateTime(Convert.ToInt32(data.Substring(4, 4)), 

                                        Convert.ToInt32(data.Substring(2, 2)),

                                        Convert.ToInt32(data.Substring(0, 2)), 

                                        Convert.ToInt32(hora.Substring(0, 2)), 

                                        Convert.ToInt32(hora.Substring(2, 2)),0);

        }

        tempo.Stop();

        Console.WriteLine("Convert = {0}ms", tempo.ElapsedMilliseconds);

        tempo.Restart();

        for (var i = 0; i < 10000; i++) {

            try {

                var dateTime = DateTime.Parse(string.Format("{0}/{1}/{2} {3}:{4}",

                data.Substring(0, 2),

                data.Substring(2, 2),

                data.Substring(4, 4),

                hora.Substring(0, 2),

                hora.Substring(2, 2)));

            } catch (FormatException ex) {

                throw ex;

            } 

        }

        tempo.Stop();

        Console.WriteLine("Parse = {0}ms", tempo.ElapsedMilliseconds);

    }

}