ASP.NET MVC入門 10、Action Filter與內置的Filter實現(實例-防盜鏈)

前一篇中我們已經了解了Action Filter與內置的Filter實現，現在我們就來 寫一個實例。就寫一個防盜鏈的Filter吧。

首先繼承自FilterAttribute 類同時實現IActionFilter接口，代碼如下：

/**//// <summary>
/// 防盜鏈Filter.
/// </summary>
public class AntiOutSiteLinkAttribute : ActionFilterAttribute, IActionFilter
{
    public AntiOutSiteLinkAttribute(FileType fileType)
    {
        this.FileType = fileType;
    }
    /**//// <summary>
    /// 請求的文件類型.(文件或圖片)
    /// </summary>
    public FileType FileType { get; set; }
    IActionFilter 成員#region IActionFilter 成員
    void IActionFilter.OnActionExecuting(ActionExecutingContext filterContext)
    {
        HttpContextBase httpContext = filterContext.HttpContext;
        if (null != httpContext.Request.UrlReferrer)
        {
            string serverDomain = httpContext.Request.Url.Host;
            string refDomain = httpContext.Request.UrlReferrer.Host;
            if (GetRootDomain(refDomain).Equals(GetRootDomain(serverDomain), StringComparison.OrdinalIgnoreCase))
            {
                return;//如果根域名相同就返回
            }
        }
        ContentResult cr = new ContentResult();
        if (FileType == FileType.Image)
        {
            cr.ContentType = "image/jpeg";
            FileInfo fi = new FileInfo(httpContext.Server.MapPath("~/Content/images/outsitelink.jpg"));
            if (fi.Exists)
            {
                httpContext.Response.WriteFile(fi.FullName);
            }
            else
            {
                Bitmap bmp = new Bitmap(200, 50);
                Graphics g = Graphics.FromImage(bmp);
                g.FillRectangle(Brushes.White, 0, 0, 200, 50);
                g.DrawString("請不要盜鏈", new Font("Arial", 15), Brushes.Red, new PointF(0, 0));
                bmp.Save(httpContext.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Gif);
            }
        }
        else
        {
            cr.ContentType = "text/html";
            cr.Content = string.Format("請不要盜鏈。返回<a href='{0}'>{1}</a>", Utils.AbsoluteWebRoot, BlogSettings.Instance.Name);
        }
        //將當前的上下文的ActionResult設置為我們的cr(ContentResult)
        filterContext.Result = cr;
    }
    #endregion
    /**//// <summary>
    /// 獲取網站的根域名
    /// </summary>
    /// <param name="domain">網站的域名，不帶"Http://"</param>
    /// <returns></returns>
    private string GetRootDomain(string domain)
    {
        if (string.IsNullOrEmpty(domain))
        {
            throw new ArgumentNullException("參數'domain'不能為空");
        }
        string[] arr = domain.Split(new[] { '.' }, StringSplitOptions.RemoveEmptyEntries);
        if (arr.Length <= 2)
        {
            return domain;
        }
        else
        {
            return arr[arr.Length - 2] + "." + arr[arr.Length - 1];
        }
    }
}
public enum FileType
{
    File = 1,
    Image
}