Check Upload Image size and height width using asp.net c#

protected void Btn_Upload(object sender, EventArgs e)

    {

        System.Drawing.Image img = System.Drawing.Image.FromStream(Upload_img.PostedFile.InputStream);

        int height = img.Height;

        int width = img.Width;

        decimal size = Math.Round(((decimal)Upload_img.PostedFile.ContentLength / (decimal)1024), 2);

        ScriptManager.RegisterStartupScript(Page, Page.GetType(), "alert", "alert('Size: " + size + "KB\\nHeight: " + height + "\\nWidth: " + width + "');", true);

      

    }