由于保护级别的原因,公共类无法访问;构造函数是公共的

我有一个公共类ArticleDao,但当我尝试在另一个文件中使用它时,它会显示“ArticleDa由于其保护级别而无法访问”。下面是整个类:

class ArticleDao : IArticleDao
{
    private readonly ContentManager _contentManager;

    private static readonly char[] DelimiterChars = { '|', '\n' };

    private const int ArticlePagingSize = 500;

    public ArticleDao()
    {
        _contentManager = new ContentManager();
    }

    private Image GetImage(XElement element)
    {
        var image = new Image();

        if (String.IsNullOrEmpty((String)element))
        {
            return image;
        }

        XElement imageElement = element.Element("img");
        if (imageElement != null)
        {
            image.Url = (String)imageElement.Attribute("src");
        }
        return image;
    }

    private Link GetLink(XElement element)
    {
        var link = new Link();

        if (String.IsNullOrEmpty((String)element))
        {
            return link;
        }

        XElement anchorElement = element.Element("a");
        if (anchorElement != null)
        {
            link.Url = (String)anchorElement.Attribute("href");
            link.Text = (String)anchorElement;
        }
        return link;
    }

    public Article GetArticle(long id, string html)
    {
        var a = new Article();
        long testid = 556;
        if (id == testid)
        {
            var x = 1;
        }

        XDocument xdoc = XDocument.Parse(html);
        var xElement = xdoc.Element("root");
        if (xElement != null)
        {
            XElement articleElem = xElement.Element("Event");
            if (articleElem != null)
            {
                a = new Article();
                a.Id = id.ToString(CultureInfo.InvariantCulture);
                a.Title = (String)articleElem.Element("Title");
                a.PublishedDate = GetDateTime((String)articleElem.Element("PublishedDate"));
                a.SubHeader = (String)articleElem.Element("SubHeader");
                a.Image = GetImage(articleElem.Element("Image"));
                a.Caption = (String)articleElem.Element("Caption");
                a.Body = (String)articleElem.Element("Body");
                a.Url = GetLink(articleElem.Element("Url"));

            }
        }

        return a;

    }

    public Article GetArticle(Int64 ektronContentId)
    {
        var item = _contentManager.GetItem(ektronContentId);
        return GetArticle(ektronContentId, item.Html);
    }

    public IEnumerable<Article> GetArticles(Int64 folderId)
    {
        int count;
        IEnumerable<Article> articles = new List<Article>(ArticlePagingSize);
        do
        {
            var criteria = new ContentCriteria();
            criteria.AddFilter(ContentProperty.FolderId, CriteriaFilterOperator.EqualTo, folderId);
            criteria.PagingInfo.RecordsPerPage = ArticlePagingSize;

            var articleContentData = _contentManager.GetList(criteria);
            count = articleContentData == null ? 0 : articleContentData.Count;

            articles = articles.Concat(_contentManager.GetList(criteria)
                .Select(i => GetArticle(i.Id, i.Html)));
        } while (count == ArticlePagingSize);
        return articles;
    }

    private DateTime GetDateTime(string date)
    {
        DateTime dt;

        DateTime.TryParse(date, out dt);

        return dt;
    }
}

构造函数是公共的。我甚至尝试用“public”替换所有“private”实例,但它仍然表示无法访问。这是我试图调用它的行:

private static IArticleDao _articleDao;
public static IArticleDao ArticleDao
{
    get { return _articleDao ?? (_articleDao = new ArticleDao()); }
}

其中“_articleDao=new articleDao()”是错误所在。

我特别困惑,因为要创建ArticleDao和IArticleDao,我基本上只是复制了EventDao和IEventDao,并将“Event”替换为“Article”

private static IEventDao _eventDao;
public static IEventDao EventDao
{
    get { return _eventDao ?? (_eventDao = new EventDao()); }
}

但ArticleDao不起作用。