IsCommandAvailable Method

Implement this method to provide control over whether your external command is enabled or disabled.

Namespace: Autodesk.Revit.UI
Assembly: RevitAPIUI (in RevitAPIUI.dll) Version: 2015.0.0.0 (2015.0.0.0)


bool IsCommandAvailable(
	UIApplication applicationData,
	CategorySet selectedCategories
Visual Basic
Function IsCommandAvailable ( _
	applicationData As UIApplication, _
	selectedCategories As CategorySet _
) As Boolean
Visual C++
bool IsCommandAvailable(
	UIApplication^ applicationData, 
	CategorySet^ selectedCategories


Type: Autodesk.Revit.UI UIApplication
An ApplicationServices.Application object which contains reference to Application needed by external command.
Type: Autodesk.Revit.DB CategorySet
An list of categories of the elements which have been selected in Revit in the active document, or an empty set if no elements are selected or there is no active document.

Return Value

Indicates whether Revit should enable or disable the corresponding external command.


This callback will be called by Revit's user interface any time there is a contextual change. Therefore, the callback must be fast and is not permitted to modify the active document and be blocking in any way.

See Also