IExternalCommandAvailability.IsCommandAvailable

Public Class

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

Assembly: RevitAPIUI (in RevitAPIUI.dll) Version: 25.0.0.0 (25.0.0.0)

Syntax

bool IsCommandAvailable(
  UIApplication applicationData,
  CategorySet selectedCategories
)

Parameters

applicationData UIApplication

An ApplicationServices.Application object which contains reference to Application needed by external command.

selectedCategories 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

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

Remarks

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.