Bloom.Api.ApiRequest.RequiredParam C# (CSharp) Method

        public string RequiredParam(string name)
        {
            if (Parameters.AllKeys.Contains(name))
                return Parameters[name];
            throw new ApplicationException("The query " + _requestInfo.RawUrl + " should have parameter " + name);
        }

        /// <summary>
        /// Get a json of stats about the image. It is used to populate a tooltip when you hover over an image container
        /// </summary>
        private void HandleImageInfo(ApiRequest request)
        {
            try
            {
                var fileName = request.RequiredParam("image");
                Guard.AgainstNull(_bookSelection.CurrentSelection, "CurrentBook");
                var path = Path.Combine(_bookSelection.CurrentSelection.FolderPath, fileName);
                if (!File.Exists(path))
                {
                    // We can be fed doubly-encoded filenames.  So try to decode a second time and see if that works.
                    // See https://silbloom.myjetbrains.com/youtrack/issue/BL-3749.
                    fileName = System.Web.HttpUtility.UrlDecode(fileName);
                    path = Path.Combine(_bookSelection.CurrentSelection.FolderPath, fileName);
                }
                RequireThat.File(path).Exists();
                var fileInfo = new FileInfo(path);
                dynamic result = new ExpandoObject();
                result.name = fileName;
                result.bytes = fileInfo.Length;

                // Using a stream this way, according to one source,
                // http://stackoverflow.com/questions/552467/how-do-i-reliably-get-an-image-dimensions-in-net-without-loading-the-image,
                // supposedly avoids loading the image into memory when we only want its dimensions
                using (var stream = File.OpenRead(path))
                using (var img = Image.FromStream(stream, false, false))
                {
                    result.width = img.Width;
                    result.height = img.Height;
                    switch (img.PixelFormat)
                    {
                        case PixelFormat.Format32bppArgb:
                        case PixelFormat.Format32bppRgb:
                        case PixelFormat.Format32bppPArgb:
                            result.bitDepth = "32";
                            break;
                        case PixelFormat.Format24bppRgb:
                            result.bitDepth = "24";
                            break;
                        case PixelFormat.Format16bppArgb1555:
                        case PixelFormat.Format16bppGrayScale:
                            result.bitDepth = "16";
                            break;
                        case PixelFormat.Format8bppIndexed:
                            result.bitDepth = "8";
                            break;
                        case PixelFormat.Format1bppIndexed:
                            result.bitDepth = "1";
                            break;
                        default:
                            result.bitDepth = "unknown";
                            break;
                    }
                }
                request.ReplyWithJson((object)result);
            }
            catch (Exception e)
            {
                Logger.WriteEvent("Error in server imageInfo/: url was " + request.LocalPath());
                Logger.WriteEvent("Error in server imageInfo/: exception is " + e.Message);
                request.Failed(e.Message);
            }
        }