How to implement a custom OAuth refresh token method in MVC WebApi 2

I have created my own Login Module instead of using /token. As we can see that i am returning a refresh_token which allows my access_token to get a new one. -To access my login api i request http://localhost/api/Account/LoginUser and gets access_token, refresh_token and expiry dates.

Same as my Login Module i want to implement a RefreshToken where i can return a user new access_token with extended usage time.

What i have done so far is :

[Route("RefreshToken")]
    [AllowAnonymous]
    public  HttpResponseMessage GrantRefreshToken(OAuthGrantRefreshTokenContext context)
    {
        //enforce client binding of refresh token
        if (context.Ticket == null || context.Ticket.Identity == null || !context.Ticket.Identity.IsAuthenticated)
        {

            return new HttpResponseMessage(HttpStatusCode.OK)
            {
                Content = new ObjectContent<object>(new
                {
                    Message = "Refresh token is not valid"
                }, Configuration.Formatters.JsonFormatter)
            };
        }
        else
        { // implement logic here}

But unable to get any context.

What i am doing wrong?? and please help me to implement it.

Thanks