Set ETag for FileResult - MVC 3

Question

MVC 3 RTM. I have an action that returns a file (image/jpeg). I am trying to set the ETag for a file with no success (the etag doesn't come through on header). I have tried both Response.Cache.SetETag and Response.AppenderHeader. If I add my own custom header tag, it works as expected, it just seems to be ETag that I can't set.

Here is the source.

        [HttpGet, OutputCache(Location= OutputCacheLocation.Client, VaryByParam="userId", Duration=3600, NoStore=true)]
        public ActionResult GetImage(string userId)
        {
            byte[] result;

            using (var client = new WebClient())
            {
                client.Credentials = CredentialCache.DefaultCredentials; 
                result = client.DownloadData(string.Format(IntranetUrl, userId));
            }

            Response.Cache.SetETag("00amyWGct0y_ze4lIsj2Mw");
            //or Response.AppendHeader("ETag", "00amyWGct0y_ze4lIsj2Mw");
            Response.AppendHeader("MyHeader", "HelloWorld");

            return File(result, "image/jpeg");
        }

And here is the resource request/response:

> Request
> URL:http://localhost/MyApp/Employee.mvc/GetImage?userId=myUserId
> Request Method:GET Status Code:200 OK
> Request Headers Accept:*/*
> Accept-Charset:ISO-8859-1,utf-8;q=0.7,*;q=0.3
> Accept-Encoding:gzip,deflate,sdch
> Accept-Language:en-US,en;q=0.8
> Cache-Control:max-age=0
> Connection:keep-alive
> Cookie:ASP.NET_SessionId=mySessionId
> Host:localhost
> Referer:http://localhost/MyApp/Employee/Review/24/Index
> User-Agent:Mozilla/5.0 (Windows; U;
> Windows NT 5.1; en-US)
> AppleWebKit/534.13 (KHTML, like Gecko)
> Chrome/9.0.597.98 Safari/534.13 Query
> String Parameters userId:myUserId
> Response Headers
> Cache-Control:private, no-store,
> max-age=3600 Content-Length:1428
> Content-Type:image/jpeg Date:Thu, 17
> Feb 2011 15:45:30 GMT Expires:Thu, 17
> Feb 2011 16:45:29 GMT
> Last-Modified:Thu, 17 Feb 2011
> 15:45:29 GMT MyHeader:HelloWorld
> Server:Microsoft-IIS/5.1
> X-AspNet-Version:4.0.30319
> X-AspNetMvc-Version:3.0
> X-Powered-By:ASP.NET

Update

I've stripped all the code down to this and still no go...

Action:

public FileETagActionResult GetImage()
{
    return new FileETagActionResult();
}

ActionResult:

    public class FileETagActionResult : ActionResult
    {

        public override void ExecuteResult(ControllerContext context)
        {

            byte[] result;

            using (var client = new WebClient())
            {
                result = client.DownloadData("http://myintranet/images/logo.png");
            }

            var hash = MD5.Create().ComputeHash(result);
            string etag = String.Format("\"{0}\"", Convert.ToBase64String(hash));

            TimeSpan expireTs = TimeSpan.FromDays(5);

            context.HttpContext.Response.Cache.SetCacheability(HttpCacheability.Private);
            context.HttpContext.Response.Cache.SetETag(etag);
            context.HttpContext.Response.Cache.SetExpires(DateTime.Now.AddDays(5));
            context.HttpContext.Response.Cache.SetMaxAge(expireTs);

            context.HttpContext.Response.ContentType = "image/png";
            context.HttpContext.Response.BinaryWrite(result);


        }
    }

I've created a FilePathExResult class that handles caching and byte-range support (required for video on iOS). It's super easy to use if you inherit from my base controller (just call Controller.File and everything will be handled for you). The project is BizArkWeb on CodePlex (http://bizark.codeplex.com). Sorry, no Nuget package for BizArkWeb yet. — Brian, Jul 01 '12 at 00:43

score 10 · Accepted Answer · edited May 23 '17 at 12:30

10

The ETag will be suppressed if you use HttpCacheability.Private.

You can find more information on this question

If you change it to HttpCacheability.ServerAndPrivate it should work

edited May 23 '17 at 12:30

Community

1
1

answered Mar 07 '11 at 00:24

Pedro

2,140
1
17
22

score 1 · Answer 2 · answered Feb 17 '11 at 15:59

BZ,

try doing this stuff in the ExcecuteResult override as it's too late by the time the ActionResult is being thrown back (an example from a project that i quickly opened, edit to suit):

public override void ExecuteResult(ControllerContext context)
{
    var textWriter = new StringWriter();
    var viewResult = GetViewResult(textWriter);
    viewResult.ExecuteResult(context);

    var result = textWriter.ToString()
        .RegexReplace("<script.*?>", string.Empty)
        .Replace("</script>", string.Empty);

    //#if RELEASE
    //context.HttpContext.Response.CacheControl = "Public";
    //context.HttpContext.Response.Expires = CacheDuration;
    string version = "1.0"; //your dynamic version number
    HttpCachePolicyBase cache = context.HttpContext.Response.Cache;
    TimeSpan expireTs = TimeSpan.FromDays(CacheDuration);
    cache.SetCacheability(HttpCacheability.Private);
    cache.SetETag(version);
    cache.SetExpires(DateTime.Now.Add(expireTs));
    cache.SetMaxAge(expireTs);
   //#endif

    context.HttpContext.Response.ContentType = "text/javascript";
    context.HttpContext.Response.Write(result);
}

Still no go. Wonder if it has something to do with IIS version (testing on 5.1). I can create custom headers, but Etag doesn't seem to stick around. — B Z, Feb 17 '11 at 16:42
are you setting a good expiry on the etag?? i'm afraid that for me, it just 'works (no consellation i know!!). could be the iis version i fear. — jim tollan, Feb 17 '11 at 17:04
updated my question, stripped everything down and nothing...frustrating! — B Z, Feb 17 '11 at 18:26
BZ, i'm stumped as well, can't see the problem in your approach in any way. i'll check back tmro after a nights sleep - you never know!! — jim tollan, Feb 17 '11 at 20:19

Set ETag for FileResult - MVC 3

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