Add context menu 'Edit with Paint.NET' for supported file extensions (system-wide or per-user)

pdnreg.bat

@ECHO OFF
setlocal EnableDelayedExpansion
set uninstall=no
set classkey=HKEY_CLASSES_ROOT
if [%1]==[uninstall] set uninstall=yes

net session > nul 2>&1
if %ERRORLEVEL% NEQ 0 (
 echo Setting up for current user ^(run as Administrator for system-wide change^).
 set classkey=HKEY_CURRENT_USER\Software\Classes
) else (
 echo Setting up for all users ^(run as unprivileged user for current user only^).
)

for /F tokens^=2* %%G in (
 'reg query HKEY_LOCAL_MACHINE\SOFTWARE\paint.net /v TARGETDIR ^| findstr /rc:" REG_SZ "'
) do set pdnpath=%%H

if ["%pdnpath%"]==[] (
 echo "Paint.NET installation registry keys not found. Unable to probe installation path."
 goto error
)

set pdnexec=%pdnpath%\PaintDotNet.exe
echo PDN Path: %pdnpath%

if [%uninstall%]==[yes] (
 echo ck=%classkey%
 reg query %classkey%\*\Shell\OpenPDN /ve > nul 2>&1
 if !ERRORLEVEL! EQU 0 (
  reg delete %classkey%\*\Shell\OpenPDN /f > nul 2>&1
  if !ERRORLEVEL! EQU 0 (
   echo Removed shell extension.
  ) else (
   echo Failed to remove shell extension.
  )
 ) else (
  echo Shell extension not installed at all.
 )
 goto end
)

set addexts=

for /F Tokens^=1 %%G in (
 'reg query HKEY_LOCAL_MACHINE\SOFTWARE\paint.net\Capabilities\FileAssociations ^| findstr /rc:" REG_SZ "'
) do (
 for /F "tokens=2*" %%H in (
  'reg query %classkey%\%%G /ve 2^> nul ^| findstr /rc:" REG_SZ " ^|^| reg query HKEY_CLASSES_ROOT\%%G /ve 2^> nul ^| findstr /rc:" REG_SZ " ^|^| echo x x nothing'
 ) do (
  if [%%I]==[paint.net.1] (
   echo %%G opens with Paint.NET by default -- no shell extension needed.
  ) else (
   reg query %classkey%\*\Shell\OpenPDN /ve > nul 2>&1
   if !ERRORLEVEL! EQU 0 (
    echo Shell extensions already set for %%G.
   ) else (
    set "addexts=!addexts! OR System.FileName:\"*%%G\""
    echo Should add shell extension for %%G.
   )
  )
 )
)

if not ["%addexts%"]==[""] (
 reg add %classkey%\*\Shell\OpenPDN /f /ve /t REG_SZ /d "Edit with &Paint.NET" > nul
 reg add %classkey%\*\Shell\OpenPDN /f /v Icon /t REG_SZ /d "\"%pdnexec%\",0" > nul
 reg add %classkey%\*\Shell\OpenPDN /f /v AppliesTo /t REG_SZ /d "%addexts:~4%" > nul
 reg add %classkey%\*\Shell\OpenPDN\command /f /ve /t REG_SZ /d "\"%pdnexec%\" \"%%1\"" > nul
 echo Created shell extension for Paint.NET with supported file extensions.
) else (
 echo Couldn't find extension to associate to Paint.NET.
 goto error
)
goto end

:error
exit /b 1
goto end

:end

not working if the path contains a whitespace.
change line 19 to: if ["%pdnpath%"]==[] (

In fact, I have my local copy installed in a path without spaces, thanks for the heads up!