To disable the dashboard:
defaults write com.apple.dashboard mcx-disabled -boolean YES && killall Dock
To reverse it and re-enable it:
defaults write com.apple.dashboard mcx-disabled -boolean NO && killall Dock
To disable the dashboard:
defaults write com.apple.dashboard mcx-disabled -boolean YES && killall Dock
To reverse it and re-enable it:
defaults write com.apple.dashboard mcx-disabled -boolean NO && killall Dock