Dear StackOverflow community,
For a project of mine I need to store (Temporary) data somewhere else than a Database. Actually its a little more complicated. I have a checkout page in NopCommerce where users can select them delivery moment or even location for example pickup. This data has to be store temporary untill the user made the payment. Only then I will request the data and store in DB. So that later I can retrieve the data and display in my dashboard, So that I know when the package is scheduled to be shipped.
Requirements:
Endurement: 12-24 Hours.
Store as user specific data.
Data has to be safed for quite a few sessions. Depends on the user. For example. If the user chooses a delivery moment but desides to look somewhere else before paying. This data has to be stored all those sessions.
If possible serverside.
I have quite a few options following Microsoft:
Session and state management in ASP.NET Core
Now I have tried storing data in Memory (Caching data) using 'MemoryCacheEntryOptions'. The problem is that its application wide. And its hard to maintain with hundreds of users.
Other option is 'Session state'.
The problem is that this data only endures a single session. I need to hold the data for atleast 12 to 24 hours.
Then we have 'Temp Data'. This seems like a promising option. Its great since it is kept until the is has been used/read. You even have 'Peek' and 'Keep' Methods to keep the data while peeking. Problem: It requires a controller. And requesting the data is a callback Method that doesnt require a Controller.
'Query Strings' Well its not much is it? This may be not user critical data BUT seems like query string isnt what Im looking for.
'Hidden Fields' Not really suitable either. It is therefore not form data.
'HttpContext.Items' Definetly not suitable. Data is only stored for single request.
'Cache' Way to hard to maintain user specific data.
So my question is. How do I save all this data temporary, if possible server side for a day atleast with hundreds of users at the same moment. And request the data later in a callback, to store it in DB until the order is shipped.
NopCommerce exposes a class called GenericAttributeService in Nop.Services.Common. This allows you to store your custom attribute data, specific to each customer.
To use it, first inject the GenericAttributeService into your class (controller, service class, etc).
private readonly IGenericAttributeService _genericAttributeService;
public MyFancyController(IGenericAttributeService genericAttributeService)
{
_genericAttributeService = genericAttributeService;
}
To save the data for current customer, use SaveAttribute and save an key-value pair you need:
_genericAttributeService.SaveAttribute<string>(_workContext.CurrentCustomer, "MyKeyName", "Value to save for this customer")
_genericAttributeService.SaveAttribute<int>(_workContext.CurrentCustomer, "My2ndKeyName", model.id)
To get the data use GetAttributesForEntity, where the entity is your key value.
var attribute = _genericAttributeService.GetAttributesForEntity(_workContext.CurrentCustomer.Id, "Customer").Where(x => x.Key == "MyKeyName").FirstOrDefault();
To delete the attribute use DeleteAttribute:
_genericAttributeService.DeleteAttribute(attribute);
Notice that we used _workContext which helps expose the current customer.
This already works well with other temp functionality already existing in the application, such as managing shopping carts, wish lists, etc, so browsing the source code for other examples can also be helpful.
Related
In my AppStart.cshtml I fetch some data from the database, do calculations, serialize/deserialize json strings and such, etc, and I store the result in a couple AppState-variables by doing something like the following:(C#)
AppState["myVar1"]="aString";
AppState["myVar2"]=anArray;
These variables are accessed frequently and are a bit heavy to define so I thought something like this would make sense rather than creating the data from scratch every time it's needed. Even if the optimization isn't needed it still makes sense to me since it also increases readability and definitely maintainability by not having the same code in a bunch of places where that data is needed.
Likewise, I do similar actions on a per-user basis by putting data in Session whenver a user logs in, e.g.
Session["userVar1"]="myString";
Session["userVar2"]=myAray;
However, I've just read that we should never rely on that the data stored in these still exist when we want to read them because they're stored in the server-memory which might have been cleared.
Is this true?
So when we want to access one of these we should first check whether it's null or not? And if we're lucky it's not null and we can use it straight away, otherwise we set it again.
Is this how data stored in AppState and Session are supposed to be used? And if so, what would be a good way of re-setting them if they're null? I suppose doing something like creating a function which sets them if they're null?
In your case it sounds like it's fine if the data is occasionally cleared by the server (re-starting the app process from IIS, for example) because what you've described is just a caching scenario. Cache data is inherently transient. If it's there, use it. If it's not there, re-fetch it (and populate the cache again with the result).
What I would suggest is abstracting your cache mechanism (app state and session state) from the structure of the cache itself. And within this structure you can check if the data is cached and, if not, re-cache it. Consider an object like this:
public class CacheManager
{
public static string MyString
{
get
{
if (string.IsNullOrWhiteSpace(AppState["myVar1"]))
{
// Fetch the value to be cached and set it in AppState["myVar1"]
}
return AppState["myVar1"];
}
}
}
Now anywhere in your application you can get the value by calling:
CacheManager.MyString
The rest of the application doesn't know or care if it's from app state, or session state, or a database, or a file, or any other transient location for cached data. That's entirely handled by the cache manager object. So if you ever want to change where certain values are located, you change them in that one place. Or if, for testing purposes, you want to remove the cache entirely and always get the data live, you'd just swap out the cache manager implementation with one that always returns re-fetched data. The rest of the application is blissfully unaware of the implementation.
A problem appears when two users are logged on to our service system at the same time and looking at the service list gridview. If user1 does a search to filter the gridview and user2 happens to click to another page user2 sees the results from the search performed by user1. That means one company can see another company's data.
It's an ASP.NET application that was developed in house with C#/ASP.NET 3.5. The data is stored in a SQL 2000 database and relies very heavily on stored procedures to update, select, and delete data. There are multiple user types that are restricted to what data they can see. For example, we have a company use that can only see data relavant to that company.
From what I've seen, the security is handled through If statements in the front end. Example, if userlevel = 1 then do this, if userlevel = 2 do this. These statments are used to show or hide columns in a grid, run queries to return data, and any other restrictions needed. For a company user the code behind gets the companyid assigned to the user and uses that in a query to return the results of all the data associated with that companyid (services, ships, etc).
Any recommendations for fixing this will be highly appreciated.
It's hard to say without seeing any implementation details, but on the surface it appears that there maybe some company level caching. Check for OutputCache settings, DataSource caching, explicit caching with Page.Cache, etc.
This article is a little dated, but at a glance it looks like most information is still relevant in ASP.NET 4.0.
ASP.NET Caching: Techniques and Best Practices
In addition to jrummerll's answer, check the Data Acces Layer of our app and make sure that you don't have any static variables defined. Having a static variable defined could cause this sort of issue too, since 2 contending requests may overwrite the value of the CompanyID, for example.
You basic model should work. What you've told us is not enough to diagnose the problem. But, I've got a few guesses. Most likely your code is confusing UserID or CompanyID values.
Are you mistakenly storing the CompanyID in the Cache, rather than the session?
Is the CompanyID stored in a static variable? A common (and disastrous!) pitfall in web applications is that a value stored in a static variable will remain the same for all users! In general, don't use static variables in asp.net apps.
Maybe your db caching or output caching doesn't vary properly by session or other variables. So, a 2nd user will see what was created for the previous user. Stop any caching that's happening and see if that fixes it, but debug from there.
Other variations on the above themes: maybe the query is stored in a static variable. Maybe these user-related values are stored in the cache or db, but the key for that record (UserID?) is stored in a static variable?
You can put that if statements in a thread. Threading provides you the option that only 1 user can access the application or gridview in your case.
See this link: http://msdn.microsoft.com/en-us/library/ms173179.aspx
Here is some sample code that is throughout the entire application that is used for filtering results. What is the best way to fix this so that when one user logs on, the other user doesn't see those results?
protected void PopulategvServiceRequestListing(string _whereclause)
{
_dsGlobalDatasource = new TelemarServiceRequestListing().GetServiceRequestListingDatasource(_whereclause);
if(_dsGlobalDatasource.Tables[0].Rows.Count!=0)
{
gv_ServiceRequest.DataSource = _dsGlobalDatasource;
gv_ServiceRequest.DataBind();
}
else
{
gv_ServiceRequest.DataSource=new TelemarServiceRequestListing().DummyDataset();
gv_ServiceRequest.DataBind();
gv_ServiceRequest.Rows[0].Visible = false;
gv_ServiceRequest.HeaderStyle.Font.Bold = true;
}
}
I have an ASP.NET c# project.
I have to pass a list of values (id numbers such as "23,4455,21,2,765,...) from one form to another. Since QueryString is not possible because the list could be long, which is the best way to do it?
Thanks in advance.
Thanks for all your answers, you are helping a lot !!!
I decided to do this:
On the first form:
List lRecipients = new List();
.....
Session["Recipients"] = lRecipients;
On the final form:
List lRecipients = (List)Session["Recipients"];
Session.Remove("Recipients");
You could use Session collection.
In the first page, use:
List<int> listOfInts = new List<int>();
...
Session["someKey"] = listOfInts
And in the second page, retrieve it like this:
List<int> listOfInts = Session["someKey"] as List<int>;
If your using asp.net webforms you can put it into a session variable to pass stuff from page to page. You've got to be concise of the potential performance issues of putting lots of stuff into session mind.
Session["ListOfStff"] = "15,25,44.etc";
There are any number of ways to pass this data. Which you choose will depend on your environment.
Session state is useful, but is constrained by the number of concurrent users on the system and the amount of available memory on the server. Consider this when deciding whether or not to use Session state. If you do choose session state for this operation, be sure to remove the data when you're done processing the request.
You could use a hidden input field, with runat="server" applied to it. This will make its data available server-side, and it will only last for the duration of the request. The pros of this technique are that it's accessible to both the server code and the client-side JavaScript. However, it also means that the size of your request is increased, and it may take more work to get the data where you want it (and back out).
Depending on how much data's involved, you could implement a web service to serialize the data to a temporary storage medium (say, a database table), and get back a "request handle." Then, you could pass the request handle on the query string to the next form and it could use the "handle" to fetch the data from your medium.
There are all kinds of different ways to deal with this scenario, but the best choice will depend on your environment, time to develop, and costs.
For Asp.NET MVC you can use ViewData.
ViewData["ID"] = "";
I will try to be as concise as possible. I'm using Flex/Hibernate technologies for my app. I also use Cairngorm micro-architecture for Flex. Because i'm beginner, i have probably misunderstand something about Caringorm's ModelLocator purpose. I have following problem...
Suppose that we have next data model:
USER ----------------> TOPIC -------------> COMMENT
1 M 1 M
User can start many topics, topics can have many comments etc. It is pretty simple model, just for example. In hibernate, i use EAGER fetching strategy for unidirectional USER->TOPIC and TOPIC->COMMENT relations(here is no question about best practices etc, this is just example of problem).
My ModelLocator looks like this:
...
public class ModelLocator ....
{
//private instance, private constructor, getInstance() etc...
...
//app state
public var users:ArrayCollection;
public var selectedUser:UserVO;
public var selectedTopic:TopicVO;
}
Because i use eager fetching, i can 'walk' through all object graph on my Flex client without hitting the database. This is ok as long as i don't need to insert, update, or delete some of the domain instances. But when that comes, problems with synchronization arise.
For example, if i want to show details about some user from some UserListView, when user(actor) select that user in list, i will take selected index in UserList, get element from users ArrayCollection in ModelLocator at selected index and show details about selected user.
When i want to insert new User, ok, I will save that user in database and in IResponder result method i will add that user in ModelLocator.users ArrayCollection.
But, when i want to add new topic for some user, if i still want to use convenience of EAGER fetching, i need to reload user list again... And to add topic to selected user... And if user is in some other location(indirectly), i need to insert topic there also.
Update is even worst. In that case i need to write even some logic...
My question: is this good way of using ModelLocator in Cairngorm? It seems to me that, because of mentioned, EAGER fetching is somehow pointless. In case of using EAGER fetching, synchronization on Flex client can become big problem. Should I always hit database in order to manipulate with my domain model?
EDIT:
It seems that i didn't make myself clear enough. Excuse me for that.
Ok, i use Spring in technology stack also and DTO(DVO) pattern with flex/spring (de)serializer, but i just wanted to stay out of that because i'm trying to point out how do you stay synchronized with database state in your flex app. I don't even mention multi-user scenario and poling/pushing topic which is, maybe, my solution because i use standard request-response mechanism. I didn't provide some concrete code, because this seems conceptual problem for me, and i use standard Cairngorm terms in order to explain pseudo-names which i use for class names, var names etc.
I'll try to 'simplify' again: you have flex client for administration of above mentioned domain(CRUD for each of domain classes), you have ListOfUsersView(shows list of users with basic infos about them), UserDetailsView(shows user details and list of user topics with delete option for each of topic), InsertNewUserTopicView(form to insert new topic) etc.
Each of view which displays some infos is synchronized with ModelLocator state variables, for example:
ListOfUsersView ------binded to------> users:ArrayCollection in ModelLocator
UserDetailsView ------binded to------> selectedUser:UserVO in ModelLocator
etc.
View state transition look like this:
ListOfUsersView----detailsClick---->UserDetailsView---insertTopic--->InsertTopicView
So when i click on "Details" button in ListOfUsersView, in my logic, i get index of selected row in ListOfUsers, after that i take UserVO object from users:ArrayCollection in ModelLocator at mentioned index, after that i set that UserVO object as selectedUser:UserVO in ModelLocator and after that i change view state to UserDetailsView(it shows user details and selectedUser.topics) which is synchronized with selectedUser:UserVO in ModelLocator.
Now, i click "Insert new topic" button on UserDetailsView which results in InsertTopicView form. I enter some data, click "Save topic"(after successful save, UserDetailsView is shown again) and problem arise.
Because of my EAGER-ly fetched objects, i didn't hit the database in mentioned transitions and because of that there are two places for which i need to be concerned when insert new topic for selected user: one is instance of selectedUser object in users:ArrayCollection (because my logic select users from that collection and shows them in UserDetailsView), and second is selectedUser:UserVO(in order to sync UserDetailsView which comes after successfull save operation).
So, again my question arises... Should i hit database in every transition, should i reload users:ArrayCollection and selectedUser:UserVO after save in order to synchronize database state with flex client, should i take saved topic and on client side, without hitting the database, programmatically pass all places which i need to update or...?
It seems to me that EAGER-ly fetched object with their associations is not good idea. Am i wrong?
Or, to 'simplify' :) again, what should you do in the mentioned scenario? So, you need to handle click on "Save topic" button, and now what...?
Again, i really try to explain this as plastic as possible because i'm confused with this. So, please forgive me for my long post.
From my point of view the point isn't in fetching mode itself but in client/server interaction. From my previous experience with it I've finally found some disadvantages of using pure domain objects (especially with eager fetching) for client/server interaction:
You have to pass all the child collections maybe without necessity to use them on a client side. In your case it is very likely you'll display topics and comments not for all users you get from server. The most like situation you need to display user list then display topics for one of the selected users and then comments for one of the selected topics. But in current implementation you receive all the topics and comments even if they are not needed to display. It is very possible you'll receive all your DB in a single query.
Another problem is it can be very insecure to get all the user data (or some other data) with all fields (emails, addresses, passwords, credit card numbers etc).
I think there can be other reasons not to use pure domain objects especially with eager fetching.
I suggest you to introduce some Mapper (or Assembler) layer to convert your domain objects to Data Transfer Objects aka DTO. So every query to your service layer will receive data from your DAO or Active Record and then convert it to corresponding DTO using corresponding Mapper. So you can get user list without private data and query some additional user details with a separate query.
On a client side you can use these DTOs directly or convert them into client domain objects. You can do it in your Cairngorm responders.
This way you can avoid a lot of your client side problems which you described.
For a Mapper layer you can use Dozer library or create your own lightweight mappers.
Hope this helps!
EDIT
What about your details I'd prefer to get user list with necessary displayable fields like first name and last name (to display in list). Say a list of SimpleUserRepresentationDTO.
Then if user requests user details for editing you request UserDetailsDTO for that user and fill tour selectedUser fields in model with it. The same is for topics.
The only problem is displaying list of users after user details editing. You can:
Request the whole list again. The advantage is you can display changes performed by other users. But if the list is too long it can be very ineffective to query all the users each time even if they are SimpleUserRepresentationDTO with minimal data.
When you get success from server on user details saving you can find corresponding user in model's user list and replace changed details there.
Tell you the truth, there's no good way of using Cairngorm. It's a crap framework.
I'm not too sure exactly what you mean by eager fetching (or what exactly is your problem), but whatever it is, it's still a request/response kind of deal and this shouldn't be a problem per say unless you're not doing something right; in which case I can't see your code.
As for frameworks, I recommend you look at RobotLegs or Parsley.
Look at the "dpHibernate" project. It implements "lazy loading" on the Flex client.
I am a VB.net winforms programmer attempting to build an ASP.Net app. I use data classes(objects) through reflection in most of my vb projects and was trying to adapt it to ASP.net using the VB code behind. I have a webpage that serves as an add/edit page for contact info. I instatiate my class which grabs the contact data from the data base then I have a process that loops through the controls on the form and matches up with a property in the data class. I can display data no problem. When I edit data and click the submit button my code calls a then loops through the controls on the form again and matches the control to the property of the data class to update the property of the class. However, my data class is no longer valid. I know web programming is different then winforms but I can't seem to get over the hump on this one. Is this the wrong way to go about this? Is my data class only available on the server side? Do I just reinstantiate the initial class and then loop through the propeties and change what the user changed and then call the update method (see redundant)? How can I get data class into a session object (I made an attempt in the past but was under tight deadlines and had to abandon it, maybe I need to revisit it?)?
Thanks
If you decide to keep some of your data in Session, you owe it to yourself to look at this post. Your code will be much cleaner and easier to maintain.
Yes, you need to reload the data class from the database as one option, or use an alternative approach. The reason is web is stateless, so all local variables are destroyed then the server side page unload process occurs. This means that in between requests, you need something to store your data.
You can read/write an object via the Session colleciton, as so:
Session["A"] = myobj;
myobj = (ObjType)Session["A"];
And so session stores an object for a specific user. Alternatively, cache stores application level data, so one instance of an object is available to all users (where session is unique to each user). You can make cache unique to a user by appending a user ID to the cache string.
var o = Cache.Get("A");
if (o != null) { .. }
Cache.Add("A", o, ...);
And so these mechanisms help you temporarily retain data.
You need to save your data class somewhere, usually in a session variable, otherwise it goes away as soon as the page gets sent back the user. Or else you need to recreate the data class again upon posting.