how to convert 24 hours string format to 12 hours format in c#

Use following extension method to Convert 24 hours format to 12 hours or vice versa.

using System;
using System.Globalization;

namespace NiceOne.Extensions
{
    public static class DateTimeExtentions
    {
        public static string ConvertFromToTime(this string timeHour, string inputFormat, string outputFormat)
        {
            var timeFromInput = DateTime.ParseExact(timeHour, inputFormat, null, DateTimeStyles.None);
            string timeOutput = timeFromInput.ToString(
                outputFormat,
                CultureInfo.InvariantCulture);
            return timeOutput;
        }
    }
}

Examples:

var temp = "13:30";
var temp12hour1 = temp.ConvertFromToTime("HH:mm", "h:mm tt");
var temp12hour2 = temp.ConvertFromToTime("HH:mm", "0h:mm tt");

Try following code:

string time24 = "20:15";
DateTime dt = DateTime.ParseExact(time24, "HH:mm", null, DateTimeStyles.None);;
String time12 = dt.ToString("HH:mm tt");
Console.Write(militaryDate);