How to createThumbnail Image in asp.net c3

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using BLL;
using DAL;
using System.IO;
using System.Drawing.Imaging;
namespace New_Practice.Admin
{
    public partial class AddContent : System.Web.UI.Page
    {
        public string strimg = "";
        ContentBl bl = new ContentBl();
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                if (Request.QueryString["id"] != null)
                {
                    FillData();
                }
            }
        }

        protected void btnSubmit_Click(object sender, EventArgs e)
        {
            if (Request.QueryString["id"] == null)
            {
                bl.InsertContent(txtTitle.Text, "", txtDescription.Text, chkIsActive.Checked);
                tblContent tbl = bl.SelectMaxId();
                Int32 maxid = tbl.id;
                string img = UploadImage(maxid);
                bl.UpdateContentImage(maxid, img);
                Response.Redirect("Content.aspx?flag=add");
            }
            else
            {
                if (fuImage.HasFile)
                {
                    string strImg = UploadImage(Convert.ToInt32(Request.QueryString["id"]));
                    bl.UpdateContent(Convert.ToInt32(Request.QueryString["id"]), txtTitle.Text, strImg, txtDescription.Text, chkIsActive.Checked);
                }
                else
                {
                    bl.UpdateContent(Convert.ToInt32(Request.QueryString["id"]), txtTitle.Text, hfImage.Value, txtDescription.Text, chkIsActive.Checked);
                }
            }
        }
        public string UploadImage(Int32 maxid)
        {
            string actualFolder = Server.MapPath("../Content/Full/");
            string thumbFolder = Server.MapPath("../Content/Thumb/");
            string smallFolder = Server.MapPath("../Content/Small/");
            DirectoryInfo actDir = new DirectoryInfo(actualFolder);
            DirectoryInfo thumbDir = new DirectoryInfo(thumbFolder);
            DirectoryInfo smallDir = new DirectoryInfo(smallFolder);
            if (!actDir.Exists)
            {
                Directory.CreateDirectory(actualFolder);
            }
            if (!thumbDir.Exists)
            {
                Directory.CreateDirectory(thumbFolder);
            }
            if (!smallDir.Exists)
            {
                Directory.CreateDirectory(smallFolder);
            }
            string imagename = maxid + Path.GetExtension(fuImage.PostedFile.FileName);
            string fullpath = actualFolder + imagename;
            string thumbpath = thumbFolder + imagename;
            string smallpath = smallFolder + imagename;
            if (File.Exists(fullpath))
            {
                File.Delete(fullpath);
            }
            fuImage.SaveAs(fullpath);
            ResizeImageFreeSize(fullpath, thumbpath, 320, 260, Path.GetExtension(fuImage.PostedFile.FileName));
            ResizeImageFreeSize(fullpath, smallpath, 120, 80, Path.GetExtension(fuImage.PostedFile.FileName));
            return imagename;
        }

        public static void ResizeImageFreeSize(string OriginalFile, string NewFile, int MinWidth, int MinHeight, string FileExtension)
        {
            var NewHeight = MinHeight;
            var NewWidth = MinWidth;
            var OriginalImage = System.Drawing.Image.FromFile(OriginalFile);

            if (OriginalImage.Width < MinWidth || OriginalImage.Height < MinHeight)
                throw new Exception(String.Format("Invalid Image Dimensions, please upload an image with minmum dimensions of {0}x{1}px", MinWidth.ToString(), MinHeight.ToString()));

            // If the image dimensions are the same then make the new dimensions the largest of the two mins.
            if (OriginalImage.Height == OriginalImage.Width)
                NewWidth = NewHeight = (MinWidth > MinHeight) ? MinWidth : MinHeight;
            else
            {
                if (MinWidth > MinHeight)
                    NewHeight = (int)(OriginalImage.Height * ((float)MinWidth / (float)OriginalImage.Width));
                else
                    NewWidth = (int)(OriginalImage.Width * ((float)MinHeight / (float)OriginalImage.Height));
            }

            // Just resample the Original Image into a new Bitmap
            var ResizedBitmap = new System.Drawing.Bitmap(OriginalImage, NewWidth, NewHeight);

            // Saves the new bitmap in the same format as it's source image
            FileExtension = FileExtension.ToLower().Replace(".", "");

            ImageFormat Format = null;
            switch (FileExtension)
            {
                case "jpg":
                    Format = ImageFormat.Jpeg;
                    break;
                case "gif":
                    Format = ImageFormat.Gif;
                    break;
                case "png":
                    Format = ImageFormat.Png;
                    break;
                default:
                    Format = ImageFormat.Png;
                    break;
            }

            ResizedBitmap.Save(NewFile, Format);


            // Clear handle to original file so that we can overwrite it if necessary
            OriginalImage.Dispose();
            ResizedBitmap.Dispose();
        }


        public void FillData()
        {

            tblContent tbl = new tblContent();
            tbl = bl.SelectSingle(Convert.ToInt32(Request.QueryString["id"]));
            if (tbl != null)
            {
                txtTitle.Text = tbl.title;
                hfImage.Value = tbl.img;
                txtDescription.Text = tbl.desc;
                strimg = "<a href="../Content/Thumb/" + hfImage.Value + ""  runat="server" rel="facebox">View</a>";
            }
        }
    }
}