public void HookExtension(string extensionPointName, ExtensionChangeHandler handler)
{
_extensionBuilders[extensionPointName] = handler;
//load the extensions which bundle already be active.
LoadExistingExtensions(extensionPointName, _extensionBuilders[extensionPointName]);
}
private void LoadExistingExtensions(string extensionPoint, ExtensionChangeHandler extensionChangeBuilder)
{
_extensionManager.GetExtensions(extensionPoint).ForEach(
extension => extensionChangeBuilder.Builder.Build(extension.Data, extension.Owner));
}