ContainerProperties.LockMembership Property (Visio)
Gets or sets a value that determines whether container members can be added, removed, or deleted. Read/write.
expression An expression that returns a ContainerProperties object.
For normal (non-list) containers, setting LockMembership to True does not prevent moving a container member; the container expands to include the moved member, assuming that the setting of ResizeAsNeeded is visContainerAutoResizeExpand or visContainerAutoResizeExpandContract. If ResizeAsNeeded is visContainerAutoResizeNone and you move a container member outside the outlines of the container, the shape remains a member, but the container does not expand to visibly contain it. You cannot add, remove, or delete a member from a locked container.
For list containers, setting LockMembership to True locks container members that are also list members, which prevents moving them and thus reordering of the members. It does not, however, prevent you from moving normal (non-list) members of the container out of the list (although not out of the container). You can also delete normal members.
The setting of the LockMembership property corresponds to the setting of Lock Container in the Membership group on the Container Tools Format tab.