How to create reminder in C#.NET Windows application?

using System;
using System.ComponentModel.DataAnnotations;
using Microsoft.Ajax.Utilities;
namespace AppointmentReminders.Web.Models
{
public class Reminders
{
public static int ReminderTime = 30;
public int Id { get; set; }
[Required]
public string Name { get; set; }
[Required, Phone, Display(Name = "Phone number")]
public string PhoneNumber { get; set; }
[Required]
public DateTime Time { get; set; }
[Required]
public string Timezone { get; set; }
[Display(Name = "Created at")]
public DateTime CreatedAt { get; set; }
}
}

Note: In this appointment-reminder C#.NET Windows application, an SMS reminder is sent out to the customer to remind them of their appointment.