缓存ASHX图像响应

Question

我创建了一个ashx文件来动态生成图像缩略图。我想缓存这些图像客户端后，他们被称为第一次。

URL：

~/image.ashx?dir=user&w=25&h=25&force=yes&img=matt.jpg

代码背后：

public void ProcessRequest (HttpContext context) {
    TimeSpan refresh = new TimeSpan(0, 15, 0);
    context.Response.Cache.SetExpires(DateTime.Now.Add(refresh));
    context.Response.Cache.SetMaxAge(refresh);
    context.Response.Cache.SetCacheability(HttpCacheability.Server);
    context.Response.CacheControl = HttpCacheability.Public.ToString();
    context.Response.Cache.SetValidUntilExpires(true);

    string dir = context.Request.QueryString["dir"];
    string img = context.Request.QueryString["img"];
    bool force = context.Request.QueryString["force"] == "yes";
    double w = 0;
    double h = 0;
    ...
    context.Response.ContentType = "image/jpeg";
    thumb.Save(context.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
}

使用Chrome中的Dev工具，我可以看到以下响应头：

HTTP/1.1 200 OK
Server: ASP.NET Development Server/10.0.0.0
Date: Mon, 26 Sep 2011 19:17:31 GMT
X-AspNet-Version: 4.0.30319
Set-Cookie: .ASPXAUTH=...; path=/; HttpOnly
Cache-Control: no-cache
Pragma: no-cache
Expires: -1
Content-Type: image/jpeg
Content-Length: 902
Connection: Close

有人能告诉我为什么不使用相同的URL对多个调用进行缓存吗？任何提示都将不胜感激。

Answer 1

当然，这句话：

HttpContext.Current.Response.Cache.SetCacheability(HttpCacheability.Server);

应：

HttpContext.Current.Response.Cache.SetCacheability(HttpCacheability.Public);