How do I check that a Windows QFE/patch has been installed from c#?

What's the best way in c# to determine is a given QFE/patch has been installed?

From stackoverflow Doubt

• The most reliable way is to determine which files are impacted by the QFE and use System.Diagnostics.FileVersionInfo.GetVersionInfo(path) on each file and compare the version numbers.

  edit: I think there's a way to check the uninstall information in the registry as well, but if the QFE ever becomes part of a Service Pack or rollup package that might report false negatives

  From rpetrich

• Use WMI and inspect the Win32_QuickFixEngineering enumeration.

  From TechNet:

  strComputer = "."
  Set objWMIService = GetObject("winmgmts:" _
      & "{impersonationLevel=impersonate}!\\" & strComputer & "\root\cimv2")
  Set colQuickFixes = objWMIService.ExecQuery _
      ("Select * from Win32_QuickFixEngineering")
  For Each objQuickFix in colQuickFixes
      Wscript.Echo "Computer: " & objQuickFix.CSName
      Wscript.Echo "Description: " & objQuickFix.Description
      Wscript.Echo "Hot Fix ID: " & objQuickFix.HotFixID
      Wscript.Echo "Installation Date: " & objQuickFix.InstallDate
      Wscript.Echo "Installed By: " & objQuickFix.InstalledBy
  Next
  

  The HotFixID is what you want to examine.

  Here's the output on my system:

      Hot Fix ID: KB941569
      Description: Security Update for Windows XP (KB941569)
      Hot Fix ID: KB937143-IE7
      Description: Security Update for Windows Internet Explorer 7 (KB937143)
      Hot Fix ID: KB938127-IE7
      Description: Security Update for Windows Internet Explorer 7 (KB938127)
      Hot Fix ID: KB939653-IE7
      Description: Security Update for Windows Internet Explorer 7 (KB939653)
      Hot Fix ID: KB942615-IE7
      Description: Security Update for Windows Internet Explorer 7 (KB942615)
      Hot Fix ID: KB944533-IE7
      Description: Security Update for Windows Internet Explorer 7 (KB944533)
      Hot Fix ID: KB947864-IE7
      Description: Hotfix for Windows Internet Explorer 7 (KB947864)
      Hot Fix ID: KB950759-IE7
      Description: Security Update for Windows Internet Explorer 7 (KB950759)
      Hot Fix ID: KB953838-IE7
      Description: Security Update for Windows Internet Explorer 7 (KB953838)
      Hot Fix ID: MSCompPackV1
      Description: Microsoft Compression Client Pack 1.0 for Windows XP
      Hot Fix ID: KB873339
      Description: Windows XP Hotfix - KB873339
      Hot Fix ID: KB885835
      Description: Windows XP Hotfix - KB885835
      Hot Fix ID: KB885836
      Description: Windows XP Hotfix - KB885836
      Hot Fix ID: KB886185
      Description: Windows XP Hotfix - KB886185
      Hot Fix ID: KB887472
      Description: Windows XP Hotfix - KB887472
      Hot Fix ID: KB888302
      Description: Windows XP Hotfix - KB888302
      Hot Fix ID: KB890046
      Description: Security Update for Windows XP (KB890046)
  

  From Bob King