How to generate and auto increment id with entity framework

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Linq;
using System.Web;

namespace TwoFactorAuthentication.API.Models
{
    public class leave
    {
        [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity), Key()]
        public int Id { get; set; }
        public DateTime date { get; set; }
        public decimal length_hours { get; set; }
        public decimal lenght_days { get; set; }
        public int status { get; set; }
        public string comments { get; set; }
        public int leave_request_id { get; set; }
        [Required(ErrorMessage = "Leave Type ID")]
        public int leave_type_id { get; set; }
        public int emp_number { get; set; }
        [Required(ErrorMessage = "Start Time")]
        public DateTime start_time { get; set; }
        [Required(ErrorMessage = "End Time")]
        public DateTime end_time { get; set; }
        public int duration_type { get; set; }
    }
    public class leave_request
    {
        
        [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity), Key()]
        public int id { get; set; }
        public DateTime date_applied { get; set; }
        public int leave_type_id { get; set; }
        public int emp_number { get; set; }
        public string comments { get; set; }


    }
}

SELECT * FROM hrmssoft.aspnetusers;
CREATE TABLE leave_request` (
  `id` int(10) unsigned NOT NULL,
  `leave_type_id` int(10) unsigned NOT NULL,
  `date_applied` date NOT NULL,
  `emp_number` int(7) NOT NULL,
  `comments` varchar(256) DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `emp_number` (`emp_number`),
  KEY `leave_type_id` (`leave_type_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

public async Task<ihttpactionresult> CreateLeaveRequest(ohrm_leave_request leaverequest)
        {                   
            if (!ModelState.IsValid)
            {
                return BadRequest(ModelState);
            }           
            leaverequest.date_applied = DateTime.Now;
           lvcontext.ohrm_leave_request.Add(leaverequest);           
            await lvcontext.SaveChangesAsync();
            return Ok();            
        }

[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity), Key()]
        public int id { get; set; }

{  	"leave_type_id":"4",
     "emp_number":87,
     "comments":"Hello how are you !."
}