Request model null in .NET core API if input json value integer

See more:

C#

API

ASP.NET-Core

I have a situation, One of my API which was in .net WebAPI have converted to .NetCore API. The data flow architecture
is same for both i.e Controller is defined, Request comes through JSON & is binded to Model with all parameters in model
as string.

The issue here is for my old API ( Asp.net Web API) , one of my parameter MobileNo if I pass it in string or integer it accepts it
& process the flow further.

But in (.Net Core API ) it does not happens this way. If I pass Mobile no. in string it accepts the request.
but if numeric value is passed i get null object in Model.

Have provided below sample request which is accepted
& the one which is passed as null

Accepted request

{
"EmployeeCode":"1234"
"EmployeeName":"Test"
"MobileNo":"1234567890"
}

Null Model Passed for

{
"EmployeeCode":"1234"
"EmployeeName":"Test"
"MobileNo":1234567890
}

My model and controller code is below

 public class EmpRequest 
    { 
        public string EmployeeCode { get; set; } 
        public string EmployeeName { get; set; }
        public string MobileNo { get; set; }
}


[HttpPost]
        [ProducesResponseType(200)]
        [ProducesResponseType(500)]
        public async Task<IActionResult>APIGetEmployee([FromBody] EmpRequest reqModel)
        {
}

What I have tried:

I have tried to convert the value in controller

Convert.Tostring(reqModel.MobileNo )

but its not work as model itself coming is null in request.