CollectionViewSource筛选逻辑

我提出的过滤设计,充其量是笨拙的,最糟糕的是bug。这样做的目的是让基类支持一个选择列表,并让子类根据需要添加额外的过滤逻辑。

干杯, 贝里尔

public class SubjectPickerBase<T> : ViewModelBase, ISubjectPicker<T> 
    where T : class, IAvailableItem, INotifyPropertyChanged, IActivitySubject
{
    public CollectionViewSource Subjects { get; private set; }

    protected SubjectPickerBase() { }

    protected void _Initialize(IEnumerable<T> subjects, string subjectName) {
        ...

        Subjects = new CollectionViewSource { Source = subjects };
        _ApplyFilter();
    }

    protected void _ApplyFilter() {
        Subjects.View.Filter += Filter;
    }

    private bool Filter(object obj)
    {
        var subject = obj as T;
        if (ReferenceEquals(subject, null)) return false;

        NotifyPropertyChanged(() => Status);

        var isIncludedBySubclass = OnFilter(subject);
        var isIncludedByBase = subject.IsAvailable;
        return isIncludedByBase & isIncludedBySubclass;
    }

    /// <summary>Hook to allow implementing subclass to provide it's own filter logic</summary>
    protected virtual bool OnFilter(T subject) { return true; }


 }

public class ProjectSelectionViewModel : SubjectPickerBase<ProjectViewModel>
{

    public ProjectSelectionViewModel(IEnumerable<ProjectViewModel> projects) 
    {
        ...
        _Initialize(projects, Strings.ActivitySubject__Project);
    }

    public string DescriptionMatchText {
        get { return _descriptionMatchText; }
        set {
            ApplyPropertyChange<ProjectSelectionViewModel, string>(ref _descriptionMatchText, x => x.DescriptionMatchText, value);
            _ApplyFilter();
        }
    }
    private string _descriptionMatchText;

    protected override bool OnFilter(ProjectViewModel subject)
    {
        ...
        var isDescriptionMatch = subject.IsMatch_Description(DescriptionMatchText);
        return isPrefixMatch && isMidfixMatch && isSequenceNumberMatch && isDescriptionMatch;
    }

}