Feature request: Add new "Negate" property in "Trigger" and "Condition" on use Trigger scene.

Sometimes we will need to use triggers to make some "not equals to value" scenarios (most common case: value is not null), but for such scenarios it is often necessary to add additional code in the code behind to achieve (such as add a "not" property in entity, or implement IValueConverter, even invert the default value).
But It seems that just adding a "Negate" property to the `Trigger` and `Condition` can makes everything easier.

Is it possible?? Or why not?