How to send special characters in HttpPost payload c#

Question

I am making a post call to my .net core api from client using httpclient class, my api hosted on Azure. When payload passed to api comntroler method with simple data without any special charcters call get succesfully executed, but when call made with special charcters like "%`` it get reject with status code forbidden by api gateways. We cannot change Azure api gatway policy, so some how I need to change my post data content to send special charcters in post method.

Client Call Sample

using System;
class Program
{
    static void Main(string[] args)
    {
        Task.Run(() => MainAsync());
        Console.ReadLine();
    }
    static async Task MainAsync()
    {
        using (var client = new HttpClient())
        {
            client.BaseAddress = new Uri("https://postCallPoc.net");
            var emp = new Employee()
            {
                Name = "Jhon",
                Address = "%House no 20, near Clutch & Gair showroom Mumbai", 
                DOJ = DateTime.Now.Date,
                Note = "%Verificaion Pending"
            };

            var httpContent = GetSerializeContent(emp);
            var result = await client.PostAsync("/api/Employee/add", httpContent);

            Console.WriteLine(result.StatusCode); //receiving the responce as Forbidden

        }
    }

    public class Employee
    {
        public int? ID { get; set; }
        public string Name { get; set; }
        public string Address { get; set; }
        public DateTime DOJ { get; set; }
        public string Note { get; set; }
    }
}

HTPP Content Creator

private StringContent GetSerializeContent(dynamic content)
        {
            var serilizedContent = JsonConvert.SerializeObject(content);
            //var buffer = System.Text.Encoding.UTF8.GetBytes(serilizedContent);
            var result = new StringContent(serilizedContent,  System.Text.Encoding.UTF8);
            result.Headers.ContentType = new MediaTypeHeaderValue("application/json");

            return result;
        }

API Controler

using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Logging;
using System;
using DA.Common.Master;
using DataEntity;
using ApiCommon;
using Common;

namespace MasterData.Controllers
{
    [ApiController]
    [Route("api/[controller]/[action]")]
    [Consumes("application/json")]
    [Produces("application/json")]
    public class EmployeeController : ControllerBase
    {
        ILogger<EmployeeController> _logger;
        public EmployeeController( ILogger<EmployeeController> logger) 
        {
            _logger = logger;
        }


        [HttpPost]
        public ActionResult<ApiResponse> Add(Employee emp)
        {

            ApiResponse response;
            try
            {

                var dbResponce = EmpoyeeBal.Insatnce.Save(emp);
                response = new ApiResponse
                {
                    Data = dbResponce
                };

                return Ok(response);


            }
            catch (Exception ex)
            {
                _logger.Log(ex);
            }
        }

    }
}

ERROR

403 Forbidden

403 Forbidden

---

Microsoft-Azure-Application-Gateway/v2