首先继承自FilterAttribute类同时实现IActionFilter接口，代码如下：
//// <summary>
/// 防盗链Filter.
/// </summary>
public class AntiOutSiteLinkAttribute : ActionFilterAttribute, IActionFilter
{
public AntiOutSiteLinkAttribute(FileType fileType)
{
this.FileType = fileType;
} //// <summary>
/// 请求的文件类型.(文件或图片)
/// </summary>
public FileType FileType { get; set; } #region IActionFilter 成员 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(, );
Graphics g = Graphics.FromImage(bmp);
g.FillRectangle(Brushes.White, , , , );
g.DrawString("请不要盗链", new Font("Arial", ), Brushes.Red, new PointF(, ));
bmp.Save(httpContext.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Gif);
}
}
else
{
cr.ContentType = "text/html";
cr.Content = string.Format("请不要盗链。返回<a href='{0}'>{1}</a>", Utils.AbsoluteWebRoot, BlogSettings.Instance.Name);
}
//将当前的上下文的ActionResult设置为我们的cr(ContentResult)
filterContext.Result = cr;
}
#endregion //// <summary>
/// 获取网站的根域名
/// </summary>
/// <param name="domain">网站的域名，不带"Http://"</param>
/// <returns></returns>
private string GetRootDomain(string domain)
{
if (string.IsNullOrEmpty(domain))
{
throw new ArgumentNullException("参数'domain'不能为空");
}
string[] arr = domain.Split(new[] { '.' }, StringSplitOptions.RemoveEmptyEntries);
if (arr.Length <= )
{
return domain;
}
else
{
return arr[arr.Length - ] + "." + arr[arr.Length - ];
}
}
} public enum FileType
{
File = ,
Image
}
然后我们建立一个用于处理文件请求的Controller，并应用上我们刚才建立的Filter：
public class FilesController : BaseController
{
[AntiOutSiteLink(FileType.Image)]
public ActionResult Image(string file)
{
return Content("Image From 4mvc");
} [AntiOutSiteLink(FileType.File)]
public ActionResult File(string file)
{
return Content("File From 4mvc");
}
}
测试结果：
对于ActionFilter的应用是很广泛的，需要灵活运用。对于其他应用，可以参考ASP.NET MVC Action Filter - 缓存与压缩 这一篇文章。