How to add time in datetime in C#?

ok, you can simply convert string to datetime in C# and then add datetime ticks into another datetime value, as shown below

            var eventCloseTime = "4:39 PM"; //time in string
            DateTime date = DateTime.Now.Date; // get only date
            //convert time into datetime
            DateTime dateTime = DateTime.ParseExact(eventCloseTime, "h:mm tt", System.Globalization.CultureInfo.InvariantCulture);
            //add time into datetime
            var updatedDatetime = date.AddTicks(dateTime.TimeOfDay.Ticks);

Output:

07/18/2022 16:39:00

Fiddle link: https://dotnetfiddle.net/Hi3QH5

Thanks, hope it helps.