public void OpenDocument(IDocumentViewModel viewModel)
{
Argument.IsNotNull("viewModel", viewModel);
var docViewModel = (viewModel as DocumentBaseViewModel);
docViewModel.OnBeforeOpen();
//see comments up.not using Collection.Contains because it using Equals to compare
if (!Documents.Contains_CompareByReference <IDocumentViewModel>(viewModel))
{
Documents.Add(viewModel);
}
docViewModel.IsAliveClosed = false;
viewModel.IsSelected = true;
}
