How not cache an ASP.NET user control?

Question

I'm using OutputCache in my page that has a user control, but I don't want to cache this specific user control because it's related to a user login (if I access the page, I see the page as if I were authenticated with another user).

How can I do that?

Answer 1

Personally I use the VaryByCustom attribute to give logged in and logged out users different cached page views:

<%@ OutputCache VaryByCustom="IsLoggedIn" Duration="30" VaryByParam="*" %>

then in global.asax you put

public override string GetVaryByCustomString(HttpContext context,
    string arg)
{
    if (arg == "IsLoggedIn")
    {

        if (context.Request.IsAuthenticated)
        {
            return "Logged in: " + context.User.Identity.Name;
        }
        else
        {
            return "Not Logged In";
        }

    }
    else
    {
        return base.GetVaryByCustomString(context, arg);
    }

}

I am just going to throw this out there. How about the substitution control?

http://msdn.microsoft.com/en-us/library/ms228212.aspx

According to msdn website:

The Substitution control lets you create areas on the page that can be updated dynamically and then integrated into a cached page. ... The Substitution control offers a simplified solution to partial page caching for pages where the majority of the content is cached. You can output-cache the entire page, and then use Substitution controls to specify the parts of the page that are exempt from caching.

I have never used the substituion control personally, but I just happened to look it up the other day, and it sounded like it can somehow inject updated content into an otherwise cached page output.

Answer 2

You can cache a page and you can cache a user control, but you can't cache a page except for a user control. When the user control runs the entire page has to run. You have to make the output cache for the page recognise the different users.

You can use VaryByHeader="Cookie" to cache the page for each set of cookies if the user identity is stored in a cookie. You can use VaryByCustom="SomeString" and implement a check for SomeString to do your own check for user identity in the GetVaryByCustomString method in Global.asax.