private async Task LoadCatalog()
{
if ((State?.Catalog != null) && (State.Catalog.Metadatas.Count > 0))
{
return;
}
Catalog catalog = await CatalogReader.Read(
State.AppConfig.CatalogPath);
catalog.Metadatas = catalog.Metadatas
.OrderByDescending(m => m.ModifiedDate).ToList();
State.UpdateCatalog(this, catalog);
}