Get RouteData value inside WebMethod in ASP.Net URL Routing

  [System.Web.Services.WebMethod]
    public static string GetChapterDetails()
    {
        string query = "SELECT * FROM GitaDummy.dbo.Glossary WHERE Chapter_id =@ChapterId ";
        SqlCommand cmd = new SqlCommand(query);
        var id = HttpContext.Current.Request.RequestContext.RouteData.Values["ID"];
        if (id == null)
        {
            cmd.Parameters.AddWithValue("@ChapterId", 1);
        }
        else
        { 
            cmd.Parameters.AddWithValue("@ChapterId", id);
        }
        return GetData(cmd).GetXml();
    }

I am trying to get the ID but its giving me null all the time

I am then binding them in my AJAX