State Management :: Cast From Cache To Generic List Throws An Exception
Mar 17, 2011
In Asp.net application. i cache a Linq to Xml result to a Cache object. when i cast the cache object back to generic list. i get the following exception.
[A]System.Collections.Generic.List`1[CarRentalAddress] cannot be cast to [B]System.Collections.Generic.List`1[CarRentalAddress]. Type A originates from 'mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' in the context 'LoadNeither' at location 'C:WINDOWSassemblyGAC_32mscorlib2.0.0.0__b77a5c561934e089mscorlib.dll'. Type B originates from 'mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' in the context 'LoadNeither' at location 'C:WINDOWSassemblyGAC_32mscorlib2.0.0.0__b77a5c561934e089mscorlib.dll'.
My code looks like this.
if (!Page.IsPostBack) { if (Cache["xml"] == null) { DataSet ds = new DataSet(); ds.ReadXml(HttpContext.Current.Server.MapPath("~/CarRentalAddress.xml")); var grid = (from d in ds.Tables[0].AsEnumerable() orderby d.Field<string>("City") where d.Field<string>("Enabled") == "1" select new CarRentalAddress { City = d.Field<string>("City"), HotelName = d.Field<string>("HotelName"), Address = d.Field<string>("Address"), EmailID1 = d.Field<string>("EmailID1"), EmailID2 = d.Field<string>("EmailID2") }).ToList(); Cache["xml"] = grid; totalrows = grid.Count().ToString(); grdAddress.DataSource = grid; grdAddress.DataBind(); } else { //Exception is thrown by this line var grid = (List<CarRentalAddress>)Cache["xml"]; totalrows = grid.Count().ToString(); grdAddress.DataSource = grid; grdAddress.DataBind(); } }
I need to cache System.Collection.Generic.List object with expiration time
var Root = from feed in feedhotel.Descendants(ota + "HotelContent") where (feed.Attribute("HotelCode") != null) select new xmlhotel() { }; return Root.ToList();
Is it possible to cache Root.ToList() for some time....
i'm having a gridview with textboxes and i'm allowing user to enter all the textboxes and when submit button is clicked, I'm constructing the Object and adding all the rows to LIST class.,After that i'm putting that LIST elements in a session. Everything is fine, But when i try to cast the session object to LIST type and pass it to XML serialization, I cannot see the elements in the list and it is showing LIST as NULL. I can see the generated XML string with ROOT and my classname as attributes without no data.
global.asax:-I have defined a struct (my_struct)-I add a List of structs (List<my_struct>) to Application["MyList"] In default.aspx:-I have defined the exact struct (my_struct) and want to cast the Application["MyList"] object to the List of structs.
example: x = (List<my_struct>)Application["MyList"];
I receive this error "Unable to cast object of type 'System.Collections.Generic.List`1ASP.global_asax+my_struct]' to type 'System.Collections.Generic.List`1[_Default+my_struct]'
The following code listed on the bottom is a dropdown extender contained with a listview insert template. The code works fine however int VS 2008 Debug mode, its throwing the exception:Microsoft JScript runtime error: Sys.InvalidOperationException: Handler was not added through the Sys.UI.DomEvent.addHandler method.If I click ignore or continue, the taret label is properly populated with the appropriate value. Has anybody encountered this and is
System.InvalidCastException was unhandled by user code
Message=Specified cast is not valid.
Source=App_Web_donate.aspx.cdcab7d2.wqdohvu3 StackTrace: at Donate.LoadUserDetails() in C:UsersSimonDesktopLocal SitesCats ProtectionNewDonate.aspx.vb:line 261 at Donate.btnDonate30_Click(Object sender, EventArgs e) in C:UsersSimonDesktopLocal SitesCats ProtectionNewDonate.aspx.vb:line 205 at System.Web.UI.WebControls.LinkButton.OnClick(EventArgs e) at System.Web.UI.WebControls.LinkButton.RaisePostBackEvent(String eventArgument) at System.Web.UI.WebControls.LinkButton.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
InnerException: I have made the important bits Bold I have the following code which is generating this error:
[Code]....
I am not entirely sure what is causing it. Its completley intermitent. I am storing all the details of a user filling in a form in a structure, and then assigning that structure to a session variable. This means if they page back, and then page forward again, I can pre-populate the form with the details they have already filled in for their conveinience by using the above code snippet. It appears that it works for a good minute, but if I leave the browser alone any longer than roughly 60 seconds, and then try and page forward to the form again, the exception will fire. While writing this post, the exception has occured in again in firefox, but interestingly, Google Chrome doesn't seem to have this problem. It looks like I can leave chrome alone for as long as I want and it will still work.
I have some weird problem. We're using Windows Server 2008 R2 x64 (8 Cores and 8 GB RAM) with IIS 7.5 and ASP.NET MVC 2.
I always cache (simple) stuff via the context cache and it seems like 9 out of 10 immediate page refreshs the Cache["MyKey"] is always null, even though there's no memory limit set on the pool and the server has lots of free memory.
I add expiring data via:
[Code]....
When just doing: Cache.Insert("MyKey", myObject); or Cache["MyKey"] = myObject; I get the same result (cache is almost always null for that key).
As you can see I added a callback, which writes the CacheItemRemovedReason to a text file, and the text file says CacheItemRemovedReason.Removed for MyKey. The doc for CacheItemRemovedReason.Removed says, that I call Remove/Insert on it, even though in my whole project there's no "Remove"-calls, just simple if(Cache["MyKey"] == null) {Cache["MyKey"] = ...} stuff.
I have a treeview that shown groups and their sub groups in my usercontrol. I pass the parent GroupId to the usercpntrol from the page. I want to cache nodes of treeview for every Parent Group Id. My code is works good for first time and fill the cache object . after refresh the page, cache object fill the TreeNodeCollection succesfully and everything is ok. But after another refresh, cache object is not null but is empty and TreeNodeCollection.count is zero(0). What's my fault? Please help me to solve this problem.
I am looking for an elegant (i guess as elegant as it can be) solution to caching a users profile on login (whether it is session, cache, cookie, etc) and keeping it in sync when a users profile is changed. How do you guys handle this? Just simply call a Flush() method in your Save() method that invalidates the cache?
I'm trying to cache a complex page with lots of controls on it so that if the user navigates to it later it will look like it did when he last saw it.The page has controls which post back and other controls are populated depending on the selections.
I'm using [Code].... after the <@ Page directive.
What happens is that a postback gets the cached page, so no processing and it looks the same regardless of user selections. So far so good. But if I browse to another page and return by a link, the cached version is ignored and the default page is created again. This is more or less the opposite to what i want.
I attempted to use the validation callback to ensure that a postback resulted in a new version, and that worked, but it still ignored the cached page if it wasn't a postback.I realise that it will need more work to ensure each user gets their version of the page from the cache, but why bother if this doesn't work.
I know the big difference, but one thing is confusing me. Cache works only on a single machine on webfarm and to make it globally we use Velocity or memcache.So is static does same, or is it already work globally ? eg
Cache["someid"] = "value"; //this will only work on single machine cache,
static string abc = "value"; // will this work on single machine or globally ?
I wanted to know the best practice for caching data. Say I have some control example a dropdown list which is populated from my db. Now this dropdown is global and used across many pages. I was thinking of not going to database everytime to fetch data for this dropdown and put the result in Cache. And then populate this dropdown from cache. Is this a good practice or if there is another approach. Can I store my datareader in cache and then use it globally. Also could I do this in application start event?
I am working with asp.net mvc and i am trying to get acces to a object that is in the cache.In the Application_Start() of Global.asax.cs i create and store an object in the cache like this:
Translator translator = new Translator(); HttpContext.Current.Cache.Insert("Translator", translator, null, System.Web.Caching.Cache.NoAbsoluteExpiration, System.Web.Caching.Cache.NoSlidingExpiration);
Translator holds a dictionary with translations.Now i want acces to this object from the cache to use functions and get values from the dictionary.I know i can acces it like this HttpContext.Current.Cache.Get("Translator") or Cache.Get("Translator") in the views But how can i use the functions of the object ? The meaning of the cache is to have a object that is accesable througout the webapp right ?
Do i have to make an object and asses the value of the Cache.Get("Translator") to it, so i can use the functions or is there another solution?
I have a generic handler in which I fill up a Session variable. I implemented the IRequiresSessionState interface, so it shouldn't be a problem.
In a given page, I want to display that value, but it seems like the value is always empty. Is it because the session that is accessed and written to in the handler isn't the same one that is used on this page?
In the handler, I used context.Session["EID"] = "somevalue";
edit: i found out what the issue is but I do not know how to solve it. It's because I have this Java applet which reads out an eID, calls the handler to store the data, but the session used by the applet is not the same as the session used by the browser... so how could I exchange this data in a safe way?
I have added a list to the cache with an expiry date, however the expiry date doesnt work, im not sure how long the cached item lasts but its no more than a day.
I have an asp.net solution in which there are two web application projects (client website and admin website) and also a class liabrary project in the same solution . In the live production server, the admin web app is within the client app (eg: client site= [URL] and admin site=[URL]). A class (with static variables) in class liabrary is userd to cache data. My problem is that i cannot get the changes to the static cache by one web project reflected to the other (becoz, i think, they seem to load in seperate appdomains).
I am using this to store my user information for authentication. I'd like to know where this is actually being stored? I know that people suggest to store the Session state in SQL. Is this necessary for the Cache as well?
