Maintain session in subsequent request in WEB API for OTP verification

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C#

MVC

session

WebAPI

WebAPI2

I am working on one MVC application, where there is separate WEB API project also. Now I want to implement update email functionality based on OTP verification from mobile via WEB API. Web API is stateless but still, I want to implement SESSION in my code so that I can access OTP value in subsequence request and validate it. Currently, I am able to store OTP in session in the first request but in next request Session is null and I can not access stored OTP value.

I do not want database trip to store and retrieve the OTP.

public HttpResponseMessage SendOtpOnMobile([FromBody]OtpOnMobileAPIRequest objOtpOnMobileAPIRequest)
{            
    otpValue = CommonUtility.GenerateRandomOTP(4);
    HttpContext.Current.Session["otpGeneratedValue"] = otpValue;
    //Send OTP logic and response code
    ....
}

public HttpResponseMessage ValidateOtpFromMobile([FromBody]ValidateOtpFromMobileAPIRequest objValidateOtpFromMobileAPIRequest)
{
    var otpGeneratedValue = HttpContext.Current.Session["otpGeneratedValue"];
    if(objValidateOtpFromMobileAPIRequest.OTP == otpGeneratedValue)
    {
        //success
    }
    ....
}

What I have tried:

ASP.NET Web API session or something?
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Accessing Session Using ASP.NET Web API