By default, the AllowLinkObjects property is exLeftClick + exSHIFTKey, which indicates that the user can start linking two elements once he clicks an element while keeping the SHIFT key pressed. The AllowLinkObjects property specifies the combination of keys that allows the user to link the objects. Set the AllowLinkObjects property on exDisallow to prevent adding links between elements at runtime. The Background(exLinkObjectsInvalidColor) property specifies the color to show the invalid link. The Background(exLinkObjectsValidColor) property specifies the color to show the valid link. The control fires the LayoutStartChanging(exLinkObjects) / LayoutEndChanging(exLinkObjects) event when the user creates a new link on the surface.

The order of the events when the user links two elements at runtime is:

• LayoutStartChanging(exLinkObjects), the user clicks on the surface
• AllowLink, occurs to specify whether the link between two elements is possible.
• AddLink, adds the new link to the Links collection
• CreateLink, the user ends creating the link
• LayoutEndChanging(exLinkObjects), the user un-clicks the surface

The following screen shot shows the link when the user links elements: