Parameters
- toPort
By default this is true when toPort is not the same as this port, CanLinkFrom is true, and CanLinkTo is true for the toPort port. Furthermore, this considers the IsValidSelfNode, the IsValidDuplicateLinks, and the GoDocument.ValidCycle properties.
This is called by GoToolLinkingNew.GoToolLinking.IsValidLink and GoToolRelinking.GoToolLinking.IsValidLink.