ZeroInstall.Publish.Capture.SnapshotDiff.GetFileType C# (CSharp) Method

        private VerbCapability GetFileType([NotNull] string progID, [NotNull] CommandMapper commandMapper)
        {
            #region Sanity checks
            if (string.IsNullOrEmpty(progID)) throw new ArgumentNullException(nameof(progID));
            if (commandMapper == null) throw new ArgumentNullException(nameof(commandMapper));
            #endregion

            using (var progIDKey = Registry.ClassesRoot.OpenSubKey(progID))
            {
                if (progIDKey == null) return null;

                VerbCapability capability;
                if (progIDKey.GetValue(DesktopIntegration.Windows.UrlProtocol.ProtocolIndicator) == null)
                { // Normal file type
                    var fileType = new FileType {ID = progID};

                    foreach (var fileAssoc in FileAssocs.Where(fileAssoc => fileAssoc.Value == progID && !string.IsNullOrEmpty(fileAssoc.Key)))
                    {
                        using (var assocKey = Registry.ClassesRoot.OpenSubKey(fileAssoc.Key))
                        {
                            if (assocKey == null) continue;

                            fileType.Extensions.Add(new FileTypeExtension
                            {
                                Value = fileAssoc.Key,
                                MimeType = assocKey.GetValue(DesktopIntegration.Windows.FileType.RegValueContentType, "").ToString(),
                                PerceivedType = assocKey.GetValue(DesktopIntegration.Windows.FileType.RegValuePerceivedType, "").ToString()
                            });
                        }
                    }

                    capability = fileType;
                }
                else
                { // URL protocol handler
                    capability = new UrlProtocol {ID = progID};
                }

                string description = progIDKey.GetValue(DesktopIntegration.Windows.FileType.RegValueFriendlyName, "").ToString();
                if (string.IsNullOrEmpty(description)) description = progIDKey.GetValue("", "").ToString();
                capability.Descriptions.Add(description);

                capability.Verbs.AddRange(GetVerbs(progIDKey, commandMapper));

                // Only return capabilities that have verbs associated with them
                return capability.Verbs.Count == 0 ? null : capability;
            }
        }
    }