File Manipulation in asp.net

Intially i want to load the first file without passing query string, with the first file there should have next file link. Once the next link button is clicked then only have to pass the query string.

how to pass the query string from second file to end of the file,

        DirectoryInfo oImageFolderInfo = new DirectoryInfo(this.ImagePath);
        FileInfo[] oFileList = oImageFolderInfo.GetFiles("*.*");

       
        string fileName=string.Empty;

       if (Request.QueryString["filename"] != null)
        {
            fileName=(Request.QueryString["filename"]);

        }

        else
        {
            fileName = oFileList[0].Name;
        }

        HtmlImage imag = new HtmlImage();
        imag.Src = Url + fileName;
       

        HtmlAnchor nextAnchor = new HtmlAnchor();
       nextAnchor.Href=??
        nextAnchor.InnerText = "Next>>";
        
        HtmlAnchor prevAnchor = new HtmlAnchor();
        prevAnchor.Href=??
How to proceed this same upto reaching the end of the file?