選択したフィーチャから作成したレイヤーの実質範囲を取得

'引数   :IFeatureLayerDefinition  選択したフィーチャから作成したレイヤ
'戻り値 :IEnvelope                実質のレイヤ範囲
Public Function ExtentFromSelectionSet(FeatureLayer As IFeatureLayerDefinition) As IEnvelope
    Dim pFeatureLayer As IFeatureLayer
    Set pFeatureLayer = FeatureLayer
    
    Dim pSelectionSet As ISelectionSet
    Set pSelectionSet = FeatureLayer.DefinitionSelectionSet
    
    '選択したフィーチャから作成したレイヤでなければ引数のFeatureLayer範囲を返す
    If pSelectionSet Is Nothing Then
        Set ExtentFromSelectionSet = pFeatureLayer.AreaOfInterest
        Exit Function
    End If
    
    Dim pEnumGeometry As IEnumGeometry
    Set pEnumGeometry = New EnumFeatureGeometry
    
    Dim EnumGeometryBind As IEnumGeometryBind
    Set EnumGeometryBind = pEnumGeometry
    
    EnumGeometryBind.BindGeometrySource Nothing, pSelectionSet
    
    Dim pGeomFactory As IGeometryFactory
    Set pGeomFactory = New GeometryEnvironment
    
    Dim pGeometry As IGeometry
    Set pGeometry = pGeomFactory.CreateGeometryFromEnumerator(pEnumGeometry)
    
    Set ExtentFromSelectionSet = pGeometry.Envelope

End Function