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Creating Runtime Image Thumbnail (Asp.NET)

Upload an image and create thumbnail at runtime in ASP.NET

  protected void btnUpload_Click(object sender, EventArgs e)
  {
    //string _fileExtension = VirtualPathUtility.GetExtension(UploadPhoto.PostedFile.FileName);
    string _fileExtension = UploadPhoto.PostedFile.FileName.Substring (UploadPhoto.PostedFile.FileName.LastIndexOf('.'));
    if (_fileExtension != ".jpg" && _fileExtension != ".gif" && _fileExtension != ".bmp" && _fileExtension != ".png")
    {
      ltScript.Text = "Please upload images(jpeg/gif/bmp/png) files";
      return;
    }

    int _filesize = UploadPhoto.FileBytes.Length;
    if (_filesize > 200000)
    {
      ltScript.Text = "Size exeeds the limit of 200 KB, please upload a file with size of maximum 200 KB";
      return;
    }
    FileUpload userImage = (FileUpload)UploadPhoto;
    Byte[] imgByte = null;
    Byte[] _thumbByte = null;
    if (userImage.HasFile && userImage.PostedFile != null)
    {
      //To create a PostedFile
      HttpPostedFile File = UploadPhoto.PostedFile;
      //Create byte Array with file len
      imgByte = new Byte[File.ContentLength];
      //force the control to load data in array
      File.InputStream.Read(imgByte, 0, File.ContentLength);
      _thumbByte = GetThumbnail();

      DatabaseAdapter _dataadapt = new DatabaseAdapter();
      _dataadapt.UpdateUserPhoto(ID, imgByte, _thumbByte);

    }
    ltScript.Text = "File has been uploaded...";

  }
  private Byte[] GetThumbnail()
  {
    //Creating Thumbnail method
    System.Drawing.Image _image = System.Drawing.Image.FromStream
    (UploadPhoto.PostedFile.InputStream);
    float imgWidth = _image.PhysicalDimension.Width;
    float imgHeight = _image.PhysicalDimension.Height;
    float imgSize = imgHeight > imgWidth ? imgHeight : imgWidth;

    //the approximately pixel size of thumbnail image is 100 x 100 based on ratio
    float imgResize = imgSize <= 100 ? (float)1.0 : 100 / imgSize;
    imgWidth *= imgResize; imgHeight *= imgResize;
    //generating the thumbnail
    System.Drawing.Image _thumbnail = _image.GetThumbnailImage((int)imgWidth, (int)imgHeight, delegate() { return false; }, (IntPtr)0);

    // Converting Image File to byte Array
    byte[] imgBytes = null;
    try
    {
      using (MemoryStream ms = new MemoryStream())
      {
        _thumbnail.Save(ms, ImageFormat.Jpeg);
        imgBytes = ms.ToArray();
      }
    }
    catch (Exception ex) { ltLabel.Text = ex.ToString(); }
    return imgBytes;
  }