public void OnChildAdded(DataSnapshot snapshot, string previousChildName)
{
WorkspaceModel created = new WorkspaceModel(parent.workspacesReference.Child(snapshot.Key), snapshot);
int index_in = parent.workspaces.FindIndex(v => v.Id == previousChildName);
++index_in;
parent.workspaces.Insert(index_in, created);
parent.mainLayout.AddView(created.GetView(parent).GetView(), index_in);
}