Image Resize(web app):

System.Drawing.Image uploadedImage = System.Drawing.Image.FromFile(Server.MapPath(hdnUploadedLogo.Value));
            System.Drawing.Image image = GlobalOperations.ResizeImage(uploadedImage, new System.Drawing.Size(400, 300));


Resize function:
public static System.Drawing.Image ResizeImage(System.Drawing.Image sourceImage, System.Drawing.Size size)
    {
        decimal sourceImageHeight = sourceImage.Height, sourceImageWidth = sourceImage.Width, resizedImageHeight, resizedImageWidth;

        if (sourceImageHeight > sourceImageWidth)
        {
            if (sourceImageHeight > size.Height)
                resizedImageHeight = size.Height;
            else
                resizedImageHeight = sourceImageHeight;
            resizedImageWidth = (resizedImageHeight / sourceImageHeight) * sourceImageWidth;
        }
        else
        {
            if (sourceImageWidth > size.Width)
                resizedImageWidth = size.Width;
            else
                resizedImageWidth = sourceImageWidth;
            resizedImageHeight = (resizedImageWidth / sourceImageWidth) * sourceImageHeight;
        }
        System.Drawing.Image resizedImage = sourceImage.GetThumbnailImage(Convert.ToInt32(resizedImageWidth), Convert.ToInt32(resizedImageHeight), null, IntPtr.Zero);

        return resizedImage;
    }