/Get-DefaultAppAssociations Displays the list of default application associations that have been set in the specified Windows ...

/Get-DefaultAppAssociations 

  Displays the list of default application associations that have been 
  set in the specified Windows image. You can use this option to verify 
  that default application associations were successfully imported to the 
  image. 

    Examples: 
      Dism.exe /Image:C:\test\offline /Get-DefaultAppAssociations 
      Dism.exe /Online /Get-DefaultAppAssociations