OfficeTool/Services/OfficeDetector.cs

using System.Collections.Generic;
using System.Text.RegularExpressions;
using InstaSoftOfficeTool.Models;
using Microsoft.Win32;

namespace InstaSoftOfficeTool.Services
{
    public static class OfficeDetector
    {
        public static List<InstalledOffice> Detect()
        {
            var results = new List<InstalledOffice>();

            // Check Click-to-Run
            DetectClickToRun(results);

            // Check MSI-based installs
            DetectMsi(results);

            return results;
        }

        private static void DetectClickToRun(List<InstalledOffice> results)
        {
            try
            {
                using (var key = Registry.LocalMachine.OpenSubKey(
                    @"SOFTWARE\Microsoft\Office\ClickToRun\Configuration"))
                {
                    if (key == null) return;

                    var productIds = key.GetValue("ProductReleaseIds") as string;
                    var versionToReport = key.GetValue("VersionToReport") as string;

                    if (string.IsNullOrEmpty(productIds)) return;

                    // Split into individual products (e.g. "O365BusinessRetail,VisioProRetail")
                    var ids = productIds.Split(',');
                    foreach (var id in ids)
                    {
                        var trimmedId = id.Trim();
                        if (string.IsNullOrEmpty(trimmedId)) continue;

                        results.Add(new InstalledOffice
                        {
                            DisplayName = "Microsoft Office Click-to-Run (" + trimmedId + ")",
                            Version = versionToReport ?? "",
                            ProductCode = trimmedId,
                            IsClickToRun = true,
                            IsSelected = true
                        });
                    }
                }
            }
            catch { }
        }

        private static void DetectMsi(List<InstalledOffice> results)
        {
            var uninstallPaths = new[]
            {
                @"SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall",
                @"SOFTWARE\WOW6432Node\Microsoft\Windows\CurrentVersion\Uninstall"
            };

            foreach (var path in uninstallPaths)
            {
                try
                {
                    using (var key = Registry.LocalMachine.OpenSubKey(path))
                    {
                        if (key == null) continue;

                        foreach (var subKeyName in key.GetSubKeyNames())
                        {
                            using (var subKey = key.OpenSubKey(subKeyName))
                            {
                                if (subKey == null) continue;

                                var displayName = subKey.GetValue("DisplayName") as string;
                                var publisher = subKey.GetValue("Publisher") as string;

                                if (displayName != null &&
                                    publisher != null &&
                                    publisher.Contains("Microsoft") &&
                                    (displayName.Contains("Microsoft Office") ||
                                     displayName.Contains("Microsoft 365")))
                                {
                                    var version = subKey.GetValue("DisplayVersion") as string ?? "";

                                    // Skip Click-to-Run updater entries
                                    if (displayName.Contains("Click-to-Run") &&
                                        !displayName.Contains("Microsoft Office"))
                                        continue;

                                    // Only accept {GUID} product codes for MSI uninstall
                                    bool isGuid = Regex.IsMatch(subKeyName, @"^\{[0-9A-Fa-f\-]+\}$");

                                    results.Add(new InstalledOffice
                                    {
                                        DisplayName = displayName,
                                        Version = version,
                                        ProductCode = isGuid ? subKeyName : null,
                                        IsClickToRun = false,
                                        IsSelected = true
                                    });
                                }
                            }
                        }
                    }
                }
                catch { }
            }
        }
    }
}