Not sure if I understood your question correct or not, but if you want to convert utc to ist.
This works for me :
var timeZone = TimeZoneInfo.FindSystemTimeZoneById("IST");
var utcNow = DateTime.UtcNow;
var istNow = TimeZoneInfo.ConvertTime(utcNow, timeZone);
Console.WriteLine($"UTC = {utcNow} IST {istNow}");