public Task <IGridData <string> > GetAsync(GridRange gridRange, ISortOrder sortOrder = null) { var t = _session.GetGridDataAsync(_evaluation.Expression, gridRange, sortOrder); if (t == null) { // May happen when R host is not running Trace.Fail(Invariant($"{nameof(VariableViewModel)} returned null grid data")); return(Task.FromResult <IGridData <string> >(null)); } return(t); }