An interface that should be implemented to provide the implementation for a accessibility check for a Revit add-in External Command.

Namespace: Autodesk.Revit.UI
Assembly: RevitAPIUI (in RevitAPIUI.dll) Version: 21.0.0.0 (21.1.1.109)

Syntax

C#
public interface IExternalCommandAvailability
Visual Basic
Public Interface IExternalCommandAvailability
Visual C++
public interface class IExternalCommandAvailability

Remarks

This interface should share the same assembly with add-in External Command.

Examples

CopyC#
public class SampleAccessibilityCheck : IExternalCommandAvailability
{
    public bool IsCommandAvailable(Autodesk.Revit.UI.UIApplication applicationData, 
        CategorySet selectedCategories)
    {
        // Allow button click if there is no active selection
        if (selectedCategories.IsEmpty)
            return true;
        // Allow button click if there is at least one wall selected
        foreach (Category c in selectedCategories)
        {
            if (c.Id.IntegerValue == (int)BuiltInCategory.OST_Walls)
                return true;
        }
        return false;
    }
}
CopyVB.NET
Public Class SampleAccessibilityCheck
    Implements IExternalCommandAvailability
    Public Function IsCommandAvailable(applicationData As Autodesk.Revit.UI.UIApplication, selectedCategories As CategorySet) As Boolean Implements IExternalCommandAvailability.IsCommandAvailable
        ' Allow button click if there is no active selection
        If selectedCategories.IsEmpty Then
            Return True
        End If
        ' Allow button click if there is at least one wall selected
        For Each c As Category In selectedCategories
            If c.Id.IntegerValue = CInt(BuiltInCategory.OST_Walls) Then
                Return True
            End If
        Next
        Return False
    End Function
End Class

See Also