C# - Caching Through HttpContext.Current.Cache Or Just A Static?
Mar 28, 2011
Last night I wrote up my first IHttpModule to do some request processing. I'm using a regular expression to inspect the raw url. The IHttpModule will be called on every request, so it seems reasonable to do some sort of caching of the regular expression object to prevent creation of it on every request.
Now my question... what is better: use the HttpContext.Current.Cache to store the instantiated object or to use a private static Regex in my module?I'm looking forward to the reasons why. Just to clarify: the regex will never change and thus always be the same thing.
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Sep 13, 2010
I have use Nhibernate in my MVC Project by me known, Nhibernate have cache on Session and Object. now, I want use HttpContext.Current.Cache (system.web) for cache data something in project. my code same that have problem, haven't it. and that's right or wrong.
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Dec 12, 2010
I want to be able to maintain certain objects between application restarts.
To do that, I want to write specific cached items out to disk in Global.asax Application_End() function and re-load them back on Application_Start().
I currently have a cache helper class, which uses the following method to return the cached value:
return HttpContext.Current.Cache[key];
Problem: during Application_End(), HttpContext.Current is null since there is no web request (it's an automated cleanup procedure) - therefore, I cannot access .Cache[] to retrieve any of the items to save to disk.
Question: how can I access the cache items during Application_End()?
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May 4, 2010
As per title. I want to be able to save some data in a cache object but this object must be available to all users/sessions and can expire.What is the best method to achieve this in a asp.net web app?
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Dec 15, 2010
During Application_End() in Global.aspx, HttpContext.Current is null. I still want to be able to access cache - it's in memory, so want to see if I can reference it somehow to save bits to disk.
Question - is there a way to reference cache in memory somehow when HttpContext.Current is null?
Perhaps I could create a global static variable that would store pointer to cache that I could update on HTTP requests (pseudo: "static <pointer X>" = HttpRequest.Current) and retrieve a reference to cache through that pointer in Application_End()?
Is there a better way to access Cache in memory when there is no Http Request is made?
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Sep 29, 2010
TL;DR: Which is likely faster: accessing static local variable, accessing variable stored in HttpRuntime.Cache, or accessing variable stored in memcached?At work, we get about 200,000 page views/day. On our homepage, we display a promotion. This promotion is different for different users, based on their country of origin and language.
All the different promotions are defined in an XML file on each web server. We have 12 web servers all serving the same site with the same XML file. There are about 50 different promotion combinations based on country/language. We imagine we'll never have more than 200 or so (if ever) promotions (combinations) total.
The XML file may be changed at any time, out of release cycle. When it's changed, the new definitions of promotions should immediately change on the live site. Implementing the functionality for this requirement is the responsibility of another developer and I.
Originally, I wrote the code so that the contents of the XML file were parsed and then stored in a static member of a class. A FileSystemWatcher monitored changes to the file, and whenever the file was changed, the XML would be reloaded/reparsed and the static member would be updated with the new contents. Seemed like a solid, simple solution to keeping the in-memory dictionary of promotions current with the XML file. (Each server doing this indepedently with its local copy of the XML file; all XML files are the same and change at the same time.)
The other developer I was working holds a Sr. position and decided that this was no good. Instead, we should store all the promotions in each server's HttpContext.Current.Cache with a CacheDependency file dependency that automatically monitored file changes, expunging the cached promotions when the file changed. While I liked that we no longer had to use a FileSystemWatcher, I worried a little that grabbing the promotions from the volitile cache instead of a static class member would be less performant.
(Care to comment on this concern? I already gave up trying to advocate not switching to HttpRuntime.Cache.)
Later, after we began using HttpRuntime.Cache, we adopted memcached with Enyim as our .NET interface for other business problems (e.g. search results). When we did that, this Sr. Developer decided we should be using memcached instead of the HttpRuntime (HttpContext) Cache for storing promotions. Higher-ups said "yeah, sounds good", and gave him a dedicated server with memcached just for these promotions. Now he's currently implementing the changes to use memcached instead.
I'm skeptical that this is a good decision. Instead of staying in-process and grabbing this promotion data from the HttpRuntime.Cache, we're now opening a socket to a network memcached server and transmitting its value to our web server.This has to be less performant, right? Even if the cache is memcached. (I haven't had the chance to compile any performance metrics yet.)On top of that, he's going to have to engineer his own file dependency solution over memcached since it doesn't provide such a facility.
Wouldn't my original design be best? Does this strike you as overengineering? Is HttpRuntime.Cache caching or memcached caching even necessary?
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Mar 31, 2010
I've always wondered how you can access the correct state of the current http context via a static method:
HttpContext.Current.Session["foo"] = "bar";
In any other program, anywhere else, my initial assumption about working with a static accessor like this is that changing it will change it across all threads. Similarly, another thread running my change it on me while I am trying to use it.But HttpContext.Current does not behave like this. It provides the appropriate state for the given request, even through the static accessor.
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Jul 28, 2010
I am building a web application using asp.net (c#) and lingtosql. When I perform update operations on my db I update my classes. I use gridview to bind to update information. When I relay solely on the database the page's take very long to load. When I relay solely on the cache, I have old data. What workarounds do I have for have asynchronous cache updating, yet not overload the database with endless requests (I'd like to update the cache only if there has been a change in the database itself, and perform the update operation asynchronously).
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May 4, 2010
Apart from blocking other threads reading from the cache what other problems should I be thinking about when locking the cache insert method for a public facing website.
The actual data retrieval and insert into the cache should take no more than 1 second, which we can live with. More importantly i don't want multiple thread potentially all hitting the Insert method at the same time.
The sample code looks something like:
public static readonly object _syncRoot = new object();
if (HttpContext.Current.Cache["key"] == null)
{
lock (_syncRoot)
{
HttpContext.Current.Cache.Insert("key", "DATA", null, DateTime.Now.AddMinutes(5), Cache.NoSlidingExpiration, CacheItemPriority.Normal, null);
}
}
Response.Write(HttpContext.Current.Cache["key"]);
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Feb 4, 2011
Is there room for issue in the following code in terms of multiple users of the same web application? I mean, I know that a purely static string will be shared across all sessions for a single ASP.NET application, but since this explicitly refers to the Current.Session, even though it is static it seems like it would always refer to the session instance of the "current user." But an error is happening that could be explained by everyone sharing the current value of Mode and thus the most recent change overwriting everyone else's mode value. (As a background: This string is in a Helpers class that is used throughout the application. I do not want to make references to Session["Mode"] throughout the application and do not want to have to pass Session["Mode"] in every method call from an aspx.cs page.)
public static string Mode
{
get
{
var value = HttpContext.Current.Session["Mode"];
return (value ?? string.Empty).ToString();
}
set
{
HttpContext.Current.Session["Mode"] = value;
}
}
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Mar 29, 2010
Is it correct to implement my caching object like this in my controller :
[code]....
And I Use it like this :
[code]....
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Feb 26, 2010
I've got a web application that runs of a state server. It looks like soon it may need to distributed and there will be two web servers behind a load balancer.
This works great for session state but my next challenge is Cache
My application leverages heavily of cache. I understand ASP.Net 4.0 will be offering more here but nothing much has been said about the how too.
There are two challenges that I face
1). Each webserver will have its own copy of cache whereas it would be more efficient to put this to a third server the same as session state is put to state server.
2). The real challenge is keeping cache in sync if a simple dataset derived from the database is changed my code dumps that cache item and reloads the cache. That's all well on one webserver but webserver number two wont know to drop that particular cache item and reload it. This could cause some unexpected problems in the application.
For scenario number 2 I could attempt to do some smart coding so server number two knows to dump the cache and reload it.
My guess is someone else has already been here before and there's probably a better implementation approach rather than writing extra code.
Does anyone know how I could achieve the goal of keeping Cache in sync between multiple webservers or even better farm Cache management to another server?
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Mar 11, 2010
I have a static class with serveral static methods. In these methods, I'm trying to access the current thread's context using HttpContext.Current. For example:
var userName = HttpContext.Current.User.Identity.Name;
However, when I do that, I receive a NullReferenceException, the infamous "Object reference not set to an instance of an object."
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Nov 23, 2010
i'm using an example in which i can fake the session.It's for use in a unittest of a mvc controller.In the test i create a controller and then i do this:
FakeHttpContext httpctx = new FakeHttpContext(null,null,null,null,mSessionItems );
ControllerContext ctx2 = new ControllerContext(httpctx,new RouteData(), target);
here mSessionItems is my session and target is my instance of a controller,and indeed, when i'm in a controller reading this.ControllerContext.HttpContext.Session, i have a session, great!but.... i also read the session outside the controller, and there i use HttpContext.Current.Session, and that is null (or actualy, the HttpContext.Current is null).
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Mar 15, 2011
I use a Masterpage (asp.net webforms) on my site and I woluld like to implement caching of some static files, like javascript, css etc.
I've tried adding the following to my page_load (in the masterpage) but when I use Fiddler the static files are still under "no-cache".
protected void Page_Load(object sender, EventArgs e)
{
// Set cache for 1 hour on all computers and servers.
// ... Proxies, browsers, and your server will cache it.
Response.Cache.SetCacheability(HttpCacheability.Public);
Response.Cache.SetMaxAge(new TimeSpan(1, 0, 0));
}
What am i doing wrong here?
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Jan 28, 2010
Does output caching help boost the performance of asp.net mvc pages that just consist of html, css, images, and javascript?
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Jul 3, 2010
Currently I have my data cached in Datasets in a static class. I was talking to my cousin's husband, who works as a C# developer for our local Telecom company.
Basically, I'm pretty new to ASP.NET and although to me having cached data in a static class makes sense to me, when I talked to him about it, he said there might be a problem when the site goes live, as on a web server more than one instance of the class may be created.
He did say this was a theory, and it was an area he didn't know an awful lot about, so I thought I'd ask some of you ASP.NET gurus to see if what I've done is totally wrong or not.
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Aug 5, 2010
I'm wondering how HttpContext.Current gets assigned a unique instance for every request considering it's a static object?
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Oct 1, 2010
[OutputCache (Duration=20, VaryByParam="None" )]
public ActionResult display()
{}
This code cache whole page.But, my site has user infomation on top like this ASP.net. The user info "Signed as userid | Edit Profile | ..." section should be changed when user sign in/out. But rest of the page is always same and it's good to Cache.
If the above code is used, the user info on top also cached and give wrong info to user.
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Jan 23, 2010
I have a List of objects in an asp.net page. when the page loads in the browser for the first time, I fetch data from the database, create objects with those data and populate the list. All these are done inside the page load event handler. Now when the page is posted back to the page, the previous list is gone, since the variables were all freed.
How can I cache that List, so that when this page is posted back, all my objects are available?
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Feb 5, 2010
Is it safe to always assume that HttpContext.Current will be non-null in Application_PreRequestHandlerExecute?
EDIT: Assuming ASP.NET webforms (not MVC).
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Aug 20, 2010
I am getting HttpContext.Current.Session is null.Will this be a problem if we have application hosted in web farm.
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Jan 20, 2011
I have some code that works fine when I need to delete some image files from a directory on my web server:
Dim ImageURL As String = dsImages.Tables(0).Rows(iImgRow).Item("ImageURL")
Dim physicalName = Server.MapPath(ImageURL)
oUpload.DeleteFileFromServer(physicalName, iAdid, iImgID)
.but I am running into a problem when a maintenance task running in a separate thread at set intervals determines that files like the above need to be deleted:
Dim ImageURL As String = dsImage.Tables(0).Rows(i - 1).Item("ImageURL")
Dim iImgID As Integer = dsImage.Tables(0).Rows(i - 1).Item("ImageId")
Dim physicalName As String = HttpContext.Current.Server.MapPath(ImageURL)
oUpload.DeleteFileFromServer(physicalName, iAdID, iImgID)
In this latter case, HttpContext.Current.Server.MapPath(ImageURL) has a value of Nothing.Is there a way to get the full path for this case?
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Feb 12, 2011
For instance if I'm inside the Page_Load method and I want to get query string data I just do this:
public partial class Product_Detail : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
[code].....
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Jun 7, 2010
i have problem accessing HttpContext.Current.Application From global.asax its seems to be null every time i try to access it. How can i to this?
HttpContext.Current.Application.Lock();
HttpContext.Current.Application["Actions"] = "hello";
HttpContext.Current.Application.UnLock();
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