Image slider

Want to display images in slider in but function is not executing 

<asp:Image ID="img_slider" runat="server" Height="250" Width="410" alt="" /><asp:SlideShowExtender  ID="SlideShowExtender" runat="server" TargetControlID="img_slider"
                        SlideShowServiceMethod="GetImages" AutoPlay="true" PlayInterval="1000" Loop="true"></asp:SlideShowExtender>

        [WebMethod]
        [ScriptMethod]
        public  Slide[] GetImages()
        {
            List<Slide> slides = new List<Slide>();
            string path = HttpContext.Current.Server.MapPath(TopRootName + _File_Format + RootName + HashKey);
            if (path.EndsWith("\\"))
            {
                path = path.Remove(path.Length - 1);
            }
            Uri pathUri = new Uri(path, UriKind.Absolute);
            string[] files = Directory.GetFiles(path);
            foreach (string file in files)
            {
                Uri filePathUri = new Uri(file, UriKind.Absolute);
                slides.Add(new Slide
                {
                    ImagePath = pathUri.MakeRelativeUri(filePathUri).ToString()
                });
            }
            return slides.ToArray();
        }

when i write static keyword with function then it's not accepting my parameter that i am passing i MapPath()? Waiting for your response!