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iOS6 Cached POST

, 19 Nov 2012
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How to resolve cached post problem with iPhone/iPad with iOS6 update.

Introduction 

Today, as webmaster of www.doblered.net (a tennis events related site) I've received an email saying that some information is not updated on iPhone/iPad. On PC's and Mac's all works fine. Searching in google, I've found this question in a forum: http://stackoverflow.com/questions/12506897/is-safari-on-ios-6-caching-ajax-results. So, working in a solution to this problem, here is my tip, that worked for me on ASP.NET with MVC3.

Background 

Solutions given in the thread implies to alter all my actions affected in many of my controllers, so I need a global solution. The GlobalFilters class is very useful to acomplish this.

Using the code

The first thing to do is create a class inherited from ActionFilterAttribute class with this code:
Public Class GlobalActionFiltersAttribute
    Inherits ActionFilterAttribute

    Public Overrides Sub OnActionExecuting(filterContext As System.Web.Mvc.ActionExecutingContext)
        '   Detects if it is a post request.
        If filterContext.HttpContext.Request.RequestType.ToLower.Equals("post") Then
            '   Adds "no-store", "no-cache" to cache-control header and "no-cache" to pragma header.
            filterContext.HttpContext.Response.Cache.SetNoStore()
            filterContext.HttpContext.Response.Cache.SetCacheability(HttpCacheability.NoCache)
        End If
        MyBase.OnActionExecuting(filterContext)
    End Sub

End Class 

The final step is adding following code to Application_Start sub on global.asax.vb file:

GlobalFilters.Filters.Add(New GlobalActionFiltersAttribute())

As result, all response header on action requested as post in our project will look like this:

no-cache, no-store
gzip
1426
text/html; charset=utf-8
Mon, 19 Nov 2012 11:23:56 GMT
-1
no-cache
Microsoft-IIS/7.0
Accept-Encoding
ASP.NET

Points of Interest 

It's obvious that even on post requests we must specify that response must not be cached. This fact is oppossed to http specifications, saying that post requests must be revalidated always. I think that Apple skipped this rule in a try to save more battery and 3G traffic than their competitors, but it's a really very bad idea. The good thing is that I've learned to apply global filters to any action in a MVC project.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Santiago Santos Cortizo
Software Developer (Senior) Agildata Sistemas
Spain Spain
Software developer since 1985

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