ASP.NET MVC output cache with dynamic fragment

StackOverflow https://stackoverflow.com/questions/3339352

Question

How could I cache an entire page except a bit at the top which says something along the lines of "Welcome back, Matt! | Log Out" if the user is logged in and so-on?

I'm using ASP.NET MVC 2.

Was it helpful?

Solution

What you are trying to achieve is called donut-caching or cache substitution. As of ASP.NET MVC 2 there is no built in helper to support this scenario. As much as I know it was a planned feature in MVC v.1 but it was dropped somewhere in the way to the release. For more info check this links http://haacked.com/archive/2008/11/05/donut-caching-in-asp.net-mvc.aspx, Is Donut Caching working properly with ASP.NET MVC?. VaryByParam option that is mentioned by Oleg here is not a good idea in your case. If you have VaryByParam a different version of the page will be put in the cache for every different value of the parameter (in your case for every user-name). Personally I would think of caching the data, not the whole output of the page.

OTHER TIPS

Probably helps

<%@ OutputCache Duration="15" VaryByParam="*" %>

or with some other value for the VaryByParam. See http://msdn.microsoft.com/en-us/library/hdxfb6cy.aspx, http://blog.maartenballiauw.be/post/2008/06/Creating-an-ASPNET-MVC-OutputCache-ActionFilterAttribute.aspx and http://blogs.microsoft.co.il/blogs/gilf/archive/2010/07/18/asp-net-output-cache-provider.aspx.

Moreover, if you have the start page which is not user depended, it is possible to replace the start page with a very static welcome page with the empty field (hidden div) instead of "Welcome back, Matt! | Log Out". After that an ajax request for filling of the user name can be started at the client side. This kind of the welcome page page can be very good cached.

Here you have a workaround solution:

*Add the OuptutCache attribute to the Controller that manages the whole view as usually:

[OutputCache(Duration = 3600, VaryByParam = "*")]
public ActionResult Index(FormCollection formCollection)
{
   //Controller code
}

*For the part that you don't want to do caching, load it using jquery + an ajax request (with its own controller and without the OutputCache attribute):

<div id="loginContainer"></div>

$(document).ready(function() {

    $.post('controller/action', postdata, function(data) {

    if (data.success == true) {

        //Populate the container with the obtained data
    }
    });

});

The view will be retrieved from the Output Cache and, once it is loaded, a request to obtain the login info will be performed. Hopefully, it will be a very quick request and the user will not notice the delay.

Get this via nuget: http://mvcdonutcaching.codeplex.com/

Add an action for LogOnPArtial, so you can change it from Html.Partial to Html.Action in the _Layout.cshtml

@Html.Action("_LogOnPartial","Account",true)

The true is a exclude parameter that says, exclude this from caching. The action will be called even if the page it is in is cached. This is the "hole" in the donut that is not cached.

On your page, such as About.cshtml that you want cached, apply DonutOutputCache attribute. This allows the new framework to inspect the page as it's caching it, and add flags where you've excluded actions.

The nice thing is the _LogOnPartial is not cached and will refresh for different users while the rest of the page is cached and the About() action will not be run. You could even configure caching on the _LogOnPartial action you created using the DonutOutputCache attribute, but a more frequent or less frequent interval, or vary by some other param. This allows you to compose pages of partials, and the cache refreshing logic is independently configured for each partial.

IMO this tool is exactly how I imagined caching in MVC should have been implemented.

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