How to search for specific value in Registry keys

Question

How can I search for specific value in the registry keys?

For example I want to search for XXX in

HKEY_CLASSES_ROOT\\Installer\\Products
         


        

Answer 1

@Caltor your solution gave me the answer I was looking for. I welcome improvements or a completely different solution that does not involve the registry. I am working with enterprise applications on Windows 10 with devices joined to Azure AD. I want/need to use Windows Hello for devices and for HoloLens 2 in a UWP app. My problem has been getting the AAD userPrincipal name from Windows 10. After a couple days searching and trying lots of code I searched the Windows Registry for my AAD account in the Current User key and found it. With some research it appears that this information is in a specific key. Because you can be joined to multiple directories there may be more than one entry. I was not trying to solve that issue, that is done with the AAD tenant Id. I just needed the AAD userPrincipal name. My solution de-dups the return list so that I have a list of unique userPrincipal names. App users may have to select an account, this is tolerable for even HoloLens.

using Microsoft.Win32;
using System.Collections.Generic;
using System.Linq;

namespace WinReg
{
  public class WinRegistryUserFind
  {
    // Windows 10 apparently places Office/Azure AAD in the registry at this location
    // each login gets a unique key in the registry that ends with the aadrm.com and the values
    // are held in a key named Identities and the value we want is the Email data item.
    const string regKeyPath = "SOFTWARE\\Classes\\Local Settings\\Software\\Microsoft\\MSIPC";
    const string matchOnEnd = "aadrm.com";
    const string matchKey = "Identities";
    const string matchData = "Email";

    public static List GetAADuserFromRegistry()
    {
      var usersFound = new List();
      RegistryKey regKey = Registry.CurrentUser.OpenSubKey(regKeyPath);
      var programs = regKey.GetSubKeyNames();
      foreach (var program in programs)
      {
        RegistryKey subkey = regKey.OpenSubKey(program);
        if(subkey.Name.EndsWith(matchOnEnd))
        {
          var value = (subkey.OpenSubKey(matchKey) != null)? (string)subkey.OpenSubKey(matchKey).GetValue(matchData): string.Empty;
          if (string.IsNullOrEmpty(value)) continue;
          if((from user in usersFound where user == value select user).FirstOrDefault() == null)
            usersFound.Add(value) ;
        }
      }

      return usersFound;
    }
  }
}