AssemblyInstance

' Identify the difference, if any, between two assembly instances
Private Sub FindAssemblyDifferences(instance1 As AssemblyInstance, instance2 As AssemblyInstance)
    Dim doc As Autodesk.Revit.DB.Document = instance1.Document
    Dim difference As AssemblyDifference = AssemblyInstance.CompareAssemblyInstances(instance1, instance2)

    Dim diffNone As AssemblyDifferenceNone = TryCast(difference, AssemblyDifferenceNone)
    If diffNone IsNot Nothing Then
        TaskDialog.Show("Revit", "Assemblies are identical")
        Return
    End If

    Dim diffConfig As AssemblyDifferenceConfiguration = TryCast(difference, AssemblyDifferenceConfiguration)
    If diffConfig IsNot Nothing Then
        TaskDialog.Show("Revit", "Elements are not arranged in space relative to each other in the same way")
        Return
    End If

    Dim diffMemberCount As AssemblyDifferenceMemberCount = TryCast(difference, AssemblyDifferenceMemberCount)
    If diffMemberCount IsNot Nothing Then
        TaskDialog.Show("Revit", "Elements counts differ: " + diffMemberCount.Count1 + " & " + diffMemberCount.Count2)
        Return
    End If

    Dim diffNameCat As AssemblyDifferenceNamingCategory = TryCast(difference, AssemblyDifferenceNamingCategory)
    If diffNameCat IsNot Nothing Then
        Dim catInt1 As Integer = diffNameCat.NamingCategoryId1.IntegerValue
        Dim catInt2 As Integer = diffNameCat.NamingCategoryId2.IntegerValue
        TaskDialog.Show("Revit", "Naming categories differ: " + doc.Settings.Categories.get_Item(DirectCast(catInt1, BuiltInCategory)).Name + " & " + doc.Settings.Categories.get_Item(DirectCast(catInt2, BuiltInCategory)).Name)
        Return
    End If

    Dim memberDifference As AssemblyDifferenceMemberDifference = TryCast(difference, AssemblyDifferenceMemberDifference)
    If memberDifference IsNot Nothing Then
        Dim assemblyMemberDifference As AssemblyMemberDifference = TryCast(memberDifference.MemberDifference, AssemblyMemberDifference)

        Dim differentCategory As AssemblyMemberDifferentCategory = TryCast(assemblyMemberDifference, AssemblyMemberDifferentCategory)
        If differentCategory IsNot Nothing Then
            Dim int1 As Integer = differentCategory.CategoryId1.IntegerValue
            Dim int2 As Integer = differentCategory.CategoryId2.IntegerValue
            TaskDialog.Show("Revit", "Element categories differ: " + doc.Settings.Categories.get_Item(DirectCast(int1, BuiltInCategory)).Name + " & " + doc.Settings.Categories.get_Item(DirectCast(int2, BuiltInCategory)).Name)
            Return
        End If
        Dim differentGeometry As AssemblyMemberDifferentGeometry = TryCast(assemblyMemberDifference, AssemblyMemberDifferentGeometry)
        If differentGeometry IsNot Nothing Then
            TaskDialog.Show("Revit", "Member geometry differs")
            Return
        End If
        Dim differentParameters As AssemblyMemberDifferentParameters = TryCast(assemblyMemberDifference, AssemblyMemberDifferentParameters)
        If differentParameters IsNot Nothing Then
            TaskDialog.Show("Revit", "Member parameters differs")
            Return
        End If
        Dim differentType As AssemblyMemberDifferentType = TryCast(assemblyMemberDifference, AssemblyMemberDifferentType)
        If differentType IsNot Nothing Then
            TaskDialog.Show("Revit", "Element types differ: " + doc.GetElement(differentType.TypeId1).Name + " & " + doc.GetElement(differentType.TypeId2).Name)
            Return
        End If
    End If
    Return
End Sub