How to persist data in the object n memory after fetching it once from database and use it with linq

Question

Hi,
I have some data from the database around 8 to 10 records .
These records are interrelated and I need to show cascade drop down.
I want to get the records from the database using c#.
And then based on certain events on the page want to use linq over the same data without having to get the data from the data base again.
i.e 
ProductName
Product Plan
Product type
Monthly
Annually
pordA
Gold
Individual
1
5
pordA
Gold
Spouse
2
6
pordA
Silver
Individual
3
7
pordA
Silver
Spouse
4
8
Prod B
Platinum
Individual
5
9
Prod B
Platinum
Spouse
6
10
Prod B
Gold
Individual
1
5
Prod B
Gold
Spouse
2
6
pordA
Silver
Individual
3
7
pordA
Silver
Spouse
4
8
pordA
Platinum
Individual
5
9
Now on page load I want product name in drop down.
Based on the productName selected i want to show Product Plan in another drop down and based on prduct plan want to show prduct type in drop down and then the annual and monthly in drop down.
I want to get all the records of  prod A and then using  linq to object  load the drop downs instead of running query to database.
How can I keep the records available across the function calls.
Regards
Vinod

Answer 1

This is mostly a ASP.NET question. You get better answers if you post it in ASP.NET forum.
This is my answer:
Session is not a suitable choice, since each user will have a duplicate of the data. Cache is a better option.
You can put something in Cache option and retrieve it from Cache similar to using Session. This is the manual method of caching and management of the cache content is on yourself.
public List<Product> GetAll()
List<Product> products = null;
if (Cache["Products"] == null)
DataSet data = RetrieveProducts();
products = ConvertProductsDataSetToObject(data);
Cache.Insert("Products", products, null, DateTime.Now.AddMinutes(30), TimeSpan.Zero);
else
products = (List<Product>)Cache["Products"];
return products;
When putting something in the cache, you should set its expire time. But one thing that is more important over this is to clear the cache when your data is changed in the data store (e.g. database).
public void UpdateProduct()
// update product in the database
// clear the cahce, so that the next request for Products, receives a fresh copy of the data
Cache["TestItem"] = null;
Other than using cache manually, there are also some helper funcationalities that manage cache automatically for you, based on the technology you use (ASP.NET Web Forms or ASP.NET MVC). For example in ASP.NET Web Forms you can ask ASP.NET Web Forms engine
to cache the output of a User Control automatocally by adding OutputCache directive to the user control. In ASP.NET MVC you can you [OutputCache] attribute and apply it to actions.
[OutputCache(Duration = 86400, Location = OutputCacheLocation.All)]
public ActionResult Index()
var model = ProductBL.GetAll();
return View(model);
Also, there is a concept named cache dependency, by which you can specify a dependency for the item being cached. When the condition is met, the cache automatically invalidates and clears.
There are three kinds of cache dependency:
Item dependency: make cached data dependent on another cached data
File dependency: make cached data dependent on a file
Sql dependency: make cached data dependent on the result of a SQL query