manipulator disable/enable

Helix toolkit looks so great, I am trying to use it for my work assignment.

Helix toolkit WFP shows some examples. One of them is ManipulatorDemo. Displaying the rotators and translators are useful for a user. But I want some flexibility for a user to disable/enable them, so I added a name to cube1's CombinedManipulator, called Cube1Rotator, also added a double-click event to ht:HelixViewport3D (called ManipulatorViewport3D) to allow a user to toggle CanRotateY, CanRotateX, CanRotateZ. Here is the double-click event,

ManipulatorViewport3D_MouseDoubleClick(object sender, MouseButtonEventArgs e)
{
Cube1Rotator.CanRotateX = !Cube1Rotator.CanRotateX;
Cube1Rotator.CanRotateY = !Cube1Rotator.CanRotateY;
Cube1Rotator.CanRotateZ = !Cube1Rotator.CanRotateZ;
}

When I tested it, the rotators were displayed or hidden correctly. However, once double-clicking the mouse, I couldn't rotate or translate the cube1 anymore, even they were displayed.

Any idea?

Thanks in advance