I use this style when I get data from database
public class User
{
public static List<User> GetUsers()
{
List<User> users = new Users();
using ( var context = new DataContext())
{
users = context.Users.ToList();
}
return users;
}
}
After I get data from database then I want to Filter user likes this
List<User> userResultList = User.GetUsers();
userResultList.Where(u => u.IsActive == true);
But cannot filter and I get this error
The ObjectContext instance has been disposed and can no longer be used
for operations that require a connection.
My Question :
Is possible way to filter result object after DataContext disposed?
Thank you very much for every support.
Update !!!
I think it possible if I create new DbContext in method scope that I want to retrieve data
Is it good enough approach?
Example
public class User
{
public static List<User> GetUsers()
{
List<User> users = new Users();
var context = new DataContext())
users = context.Users.ToList();
return users;
}
}
I wonder if you clone the list will get around the error?
User[] L = new User[users.Count];
users.CopyTo(L);
Speculation:
What you had looks like it should work on the surface.
I wonder if the thing that is returned by ToList() is something that inherits from list, and retains some hidden context awareness inside.
I can't test this idea right now. Something to think about for later though.
Related
I am using Orchard and would like to cache data specific to an authenticated user.
When a new user logs in, or after a period of time, the database should be queried again.
I've accomplished half of this below (after 30 minutes it will query the database again):
private UserData SomeUserSpecificData()
{
var data = _cacheManager.Get("userdata",
ctx => {
ctx.Monitor(_clock.When(TimeSpan.FromMinutes(30)));
return GetDatabaseData();
});
return data;
}
But how would I force the cache to re-query the database when a new user has logged in?
I have a feeling it might involve ISignals but not sure how to implement this.
Thanks.
You're absolutely right with ISignals!
You just need to inject ISignals and use it like this:
private readonly Orchard.Caching.ISignals _signals;
private UserData SomeUserSpecificData()
{
var data = _cacheManager.Get("userdata",
ctx => {
ctx.Monitor(_clock.When(TimeSpan.FromMinutes(30)));
cts.Monitor(_signals.When("SOMETHING_HAPPENED_FOR_xyz"));
return GetDatabaseData();
});
return data;
}
What's also nice to know: You can monitor as many signals as you want.
To keep things clean I'll typically create a static class like this:
public static class CacheSignals
{
public const string SomethingHappened = "SOMETHING_HAPPENED";
public const string SomethingHappenedForUser(int userId) => string.Format("SOMETHING_HAPPENED_FOR_{0}", userId);
}
Now you can simply implement a custom EventHandler forOrchard.Users.Events.IUserEventHandler
and invalidate the cache on LoggedIn.
private readonly Orchard.Caching.ISignals _signals;
public void LoggedIn(Security.IUser user)
{
_signals.Trigger(CacheSignals.SomethingHappenedForUser(user.Id));
}
I have some custom fields on my User object that I want to access with APEX code in my VisualForce trigger. When I access it from a Formula field I get to use a nifty $User reference like this:
$User.my_prop__c
From APEX I have to query the User object by UserId like this:
[select my_prop__c from User where id = :UserInfo.getUserId()].my_prop__c;
Is there something baked into APEX already that would let me get at the user properties without the SOQL query? If not, does anyone know of a utility class for lazy loading and caching user properties so the overhead is minimal.
I would use something similar to the following code sample. It uses a singleton pattern to statically store the information in memory for the duration of your transaction. It's similar to the lazy loading that twamley proposed but I feel this is a much simpler approach.
Usage 1: UserUtil.CurrentUser.Email;
Usage 2: User someUser = UserUtil.getUser(someUserId);
This will allow you to access the same information on the current user or other users in the system. Notice the queryUsers method just returns a query result. This makes it easy to add and remove fields from your query as it is isolated in its own method keeping things simple.
Note: that this code pulls in all users when used. Most orgs do not have multiple hundreds of users so heap size shouldn't be a concern. But if it is you can just modify the queryUsers() method to only return active users or filter down based on other criteria.
public class UserUtil {
//Protected Members
private static final UserUtil instance = new UserUtil();
private Map<Id, User> mapUsers;
//Properties
public static User CurrentUser {
get { return getUser(UserInfo.getUserId()); }
}
//Constructor
private UserUtil() {
mapUsers = new Map<Id, User>(queryUsers());
}
//Public Methods
public static User getUser(Id userId) {
if (instance.mapUsers.containsKey(userId)) {
return instance.mapUsers.get(userId);
}
else {
throw new InvalidUserIdException('Unable to locate user id: ' + userId);
}
}
//Private Methods
private List<User> queryUsers() {
return [SELECT
Id
, Name
, UserName
, Email
, Alias
FROM
User];
}
//Internal Classes
public class InvalidUserIdException extends Exception {}
}
I wrote my own utility class. I'm still interested in better techniques though.
This utility class lazy loads when the first property is accessed. Update_Closed_Won_Opportunities__c and Set_Opportunities_to_Closed_Won__c are my custom fields on the User object (visible only to System Administrators so people can't upgrade their permissions).
public with sharing class MyUserInfo {
private Id userId;
private User myUser; // Hold onto the user object once we've loaded it
// Default constructor uses the active user id
public MyUserInfo() {
userId = UserInfo.getUserId();
}
// Secondary constructor accepts a user id as a parameter
public MyUserInfo(Id someOtherUserId) {
userId = someOtherUserId;
}
// Only called one time when we first need it so grab all of the custom fields now
private void LazyLoadUser() {
System.AssertNotEquals(null, userId);
myUser = [
SELECT Update_Closed_Won_Opportunities__c, Set_Opportunities_To_Closed_Won__c
FROM User
WHERE id = :userId
];
System.AssertNotEquals(null, myUser, 'Unable to load user with id ' + userId); // could return defaults instead
}
// Getters (be sure to include each field in the SOQL of LazyLoadUser)
public boolean UpdateClosedWonOpportunities { get {
if (myUser == null) LazyLoadUser();
return myUser.Update_Closed_Won_Opportunities__c;
} }
public boolean SetOpportunitiesToClosedWon { get {
if (myUser == null) LazyLoadUser();
return myUser.Set_Opportunities_To_Closed_Won__c;
} }
}
Here is my trigger utilizing that class. The first line myUserInfo = new MyUserInfo(); doesn't run any SOQL. That won't happen until the first custom get property is used. Subsequent calls don't need SOQL.
trigger LockClosedOpportunity on Opportunity (before update) {
MyUserInfo myUserInfo = new MyUserInfo();
for (Opportunity o : trigger.old)
{
if (!myUserInfo.UpdateClosedWonOpportunities && o.StageName == 'Closed Won')
trigger.newMap.get(o.Id).addError('You do not have permission to change an Opportunity after it has been set to Closed Won.');
}
for (Opportunity o : trigger.new)
{
if ( !myUserInfo.SetOpportunitiesToClosedWon && o.StageName == 'Closed Won' && trigger.oldMap.get(o.Id).StageName != 'Closed Won' )
o.addError('You do not have permission to set an Opportunity to Closed Won.');
}
}
It reads similar to $User in formulas and I don't have to worry about tacking on multiple SOQL calls when one (or zero) suffices.
In MVC3 Code First EF how do you associate one entity with another without creating a new one (many-to-many)?
So I have a many-to-many relationship between class1 and class2. I need class1 to hold many class2 and vice versa. However, class2 is independent; I have a list of them that I want to edit separately and then associate with a new class1.
When I pass my class2List to the controller( via AJAX and JSON), I checked and all the Ids of the class2s correspond to existing ids in the db, i.e. new class2s are not created.
Model
class
{
[key]
public int Id {set; get;}
}
class1 : class
{
private ICollection<class2> _class2s;
public virtual ICollection<class2> class2s
{
get { return _class2s ?? ( _class2s = new HashSet<class2>()); }
set { _class2s = value; }
}
}
class2 : class
{
private ICollection<class1> _class1s;
public virtual ICollection<class1> class1s
{
get { return _class1s ?? ( _class1s = new HashSet<class1>()); }
set { _class1s = value; }
}
}
Controller
public ActionResult SaveChanges(List<class2> class2List)
{
createNewClass2AndAssociateExistingClass2s(class2List);
SaveChangesToDb();
return View("ProductDetail", Model);
}
createNewClass2AndAssociateExistingClass2s(List<class2> class2List)
{
var newClass1 = newClass1()
{
class2s = class2List;
}
////UnitOfWork allows me to access several DbSets in one transaction
unitOfWork.Create(newClass1)
}
SaveChangesToDb()
{
unitOfWork.Commit();
}
What this does is create a new class1 (as it should) but instead of associating the existing class2s with it, it makes new class2s with new Ids and adds them to the database.
My question:
Does this have to do with how EF is reading my Id property from base class?
How would I be able to associate several existing class2s as a list with a new class1, without creating new class2s in the database?
Cheers
Ok so two things I learned from figuring this out:
I was inheriting from an abstract class when I should have been implementing an interface. This is a great idea if you have several entities that have a similar property such as "Id" and you want to do something like
T FindById<T>(int id) where T : IEntity
When making associations in EF, even if the Id matches an existing entry, it will not update that entry, unless EF is tracking that entry in the context, as it says here. What I needed to do was:
Add a method in the mapping layer that gets the entry by id that I
want from the repository
Copy the attributes of the new entry into that context entry
Return the context entry
Hope this helps someone
I have a question.
My question actually extends from this one:
Shortly - what I want to get: 3 models, and 1 super model for this specific view. This super model fills(properly) IENumerable, IENumerable, IENumerable, to use them in View part. (as far as I understand it, at least...)
In this other topic Dan Revell proposed verry nice and elegant solution, but this solution does not fetch data from DB itself...
Question:
What must be done to get data in this model from DB, not from "new" instance constructors?
While using this approach tried to fetch data from DBContext. And got some problems in it ) I can't understand when (or how) to create my DBContext... Or how to access one that is created by application...
Tried to create it forcefully in Controller, like
using (var Db = new thetaskermvc.Models.TaskerDBContext())
{
var themodel = new thetaskermvc.Models.TotalView();
//Jobbers
themodel.Jobberz = new Dictionary<int, thetaskermvc.Models.Jobbers>();
var jobbers = from Jobbers in Db.Jobbers.OrderBy(g => g.jobb_name) select Jobbers;
foreach (Models.Jobbers ad in jobbers)
{
themodel.Jobberz.Add(ad.jobb_id,
new Models.Jobbers(ad.jobb_id, ad.jobb_name, ad.jobb_from, ad.jobb_carma, ad.jobb_status, ad.jobb_balance, ad.jobb_time));
}
if (themodel.Jobberz.Count == 0)
{
themodel.Jobberz.Add(-1, new Models.Jobbers(0, "NOTHING FOUND",DateTime.Now,0,"",0,0));
}
}
But as created that way Context stops it's existence (?) after passing data away from controller - I can't use it any other way but to get all data inside this controller, and fill data in model by direct add into collections in it (while use of IENumerable would fetch data on-demand, as far as I get it).
So.. If it ain't hard please enlighten me about - is it Ok to use such approach, or there is some other "common" way? Becaus beside it's clumsiness - this approach works...
PS I'm quite new to Asp, yet...
I have one view model per view with data from multiple tables (if required). On my view I have data that needs to be loaded from 2 different database tables. In my grant application controller I have the following:
private readonly IBankService bankService;
private readonly IAccountTypeService accountTypeService;
public GrantApplicationController(IBankService bankService, IAccountTypeService accountTypeService)
{
// Check incoming parameters for null values
this.bankService = bankService;
this.accountTypeService = accountTypeService;
}
In my Create action method I populate my banks and account types (to be used in drop downs) like this (different tables):
public ActionResult Create()
{
GrantApplicationCreateViewModel viewModel = new GrantApplicationCreateViewModel
{
Banks = bankService.FindAll(),
AccountTypes = accountTypeService.FindAll()
}
// Do what ever else you need to get done
return View(viewModel);
}
My partial view model would like this:
public class GrantApplicationCreateViewModel
{
public int BankId { get; set; }
public IEnumerable<Bank> Banks { get; set; }
public int AccountTypeId { get; set; }
public IEnumerable<AccountType> AccountTypes { get; set; }
// Other properties
}
In my repository class I would use the database context like this (I use Entity Framework code first):
public class BankRepository : IBankRepository
{
HefContext db = new HefContext
public IEnumerable<Bank> FindAll()
{
return db.Banks.OrderBy(x => x.Name);
}
}
In my database context class:
public class HefContext : DbContext
{
public DbSet<Bank> Banks { get; set; }
public DbSet<AccountType> AccountTypes { get; set; }
}
Doing it this way you can have one view model that has data from multiple sources. I hope this answers your question? If you need more explanation please let me know :)
You may want to have a look at this post, it explains (with a sample project) how an ideal MVC application architecture should be.
In your code sample above, your shouldn't have any references to DbContexts in a controller. Controller's job is to control the flow of requests not to connect to the DB and perform Model population.
I'm using EF 4.1 to build a domain model. I have a Task class with a Validate(string userCode) method and in it I want to ensure the user code maps to a valid user in the database, so:
public static bool Validate(string userCode)
{
IDbSet<User> users = db.Set<User>();
var results = from u in users
where u.UserCode.Equals(userCode)
select u;
return results.FirstOrDefault() != null;
}
I can use Moq to mock IDbSet no problem. But ran into trouble with the Where call:
User user = new User { UserCode = "abc" };
IList<User> list = new List<User> { user };
var users = new Mock<IDbSet<User>>();
users.Setup(x => x.Where(It.IsAny<Expression<Func<User, bool>>>())).Returns(list.AsQueryable);
Initialization method JLTi.iRIS3.Tests.TaskTest.SetUp threw exception.
System.NotSupportedException: System.NotSupportedException: Expression
references a method that does not belong to the mocked object:
x => x.Where<User>(It.IsAny<Expression`1>()).
Other than creating a level of indirection (eg, using a ServiceLocator to get an object that runs the LINQ and then mock that method) I can't think of how else to test this, but I want to make sure there is no way before I introduce another layer. And I can see this kind of LINQ queries will be needed quite often so the service objects can quickly spiral out of control.
Could some kind soul help? Thanks!
There is an article on MSDN highlighting how to mock using moq:
The gist of it is to represent linq to entities operations with linq to objects.
var mockSet = new Mock<DbSet<Blog>>();
mockSet.As<IQueryable<Blog>>().Setup(m => m.Provider).Returns(data.Provider);
mockSet.As<IQueryable<Blog>>().Setup(m => m.Expression).Returns(data.Expression);
mockSet.As<IQueryable<Blog>>().Setup(m => m.ElementType).Returns(data.ElementType);
mockSet.As<IQueryable<Blog>>().Setup(m => m.GetEnumerator()).Returns(data.GetEnumerator());
As Ladislav points out there are disadvantages to this as Linq To Objects is simply different to Linq to Entities so it may result in false positives. But it now being an MSDN article it does point that it is at least possible and perhaps recommended in some cases?
One thing that may of changed since the original answers to this post is that the Entity Framework team have opened up areas of Entity Framework in EF 6.0 to make it easier to mock it's inners.
Although I have not tried this, because IDBSet implements IEnumerable you might have to mock the enumerator method so the linq statements will pick up your list of users. You don't actually want to mock linq but by the looks of your code you want to test whether you are finding the right user based on the UserCode which I think is a valid unit test.
var user = new User { UserCode = "abc" };
var list = new List<User> { user };
var users = new Mock<IDbSet<User>>();
users.Setup(x => x.GetEnumerator()).Returns(list.GetEnumerator());
You might get a conflict with the non-generic version of the GetEnumerator but it this might help you on the right track.
Then you have to then place the mocked object on the data context which depends on other code that we don't see.
As I know Moq is able to set up only virtual methods of mocked object itself but you are trying to set up extensions (static) method - no way! These methods are absolutely outside of your mock scope.
Moreover that code is hard to test and requires too much initialization to be able to test it. Use this instead:
internal virtual IQueryable<User> GetUserSet()
{
return db.Set<User>();
}
public bool Validate(string userCode)
{
IQueryable<User> users = GetUserSet();
var results = from u in users
where u.UserCode.Equals(userCode)
select u;
return results.FirstOrDefault() != null;
}
You will just need to set up GetUserSet to return your list. Such testing has some major issues:
You are not testing the real implementation - in case of EF mocking sets is stupid approach because once you do it you change linq-to-entities to linq-to-objects. Those two are totally different and linq-to-entities is only small subset of linq-to-objects = your unit tests can pass with linq-to-objects but your code will fail at runtime.
Once you use this approach you cannot use Include because include is dependent on DbQuery / DbSet. Again you need integration test to use it.
This doesn't test that your lazy loading works
The better approach is removing your linq queries from Validate method - just call them as another virtual method of the object. Unit test your Validate method with mocked query methods and use integration tests to test queries themselves.
I found it easier just to write the stub:
internal class FakeDbSet<T> : IDbSet<T>where T : class
{
readonly HashSet<T> _data;
readonly IQueryable _query;
public FakeDbSet()
{
_data = new HashSet<T>();
_query = _data.AsQueryable();
}
public virtual T Find(params object[] keyValues)
{
throw new NotImplementedException("Derive from FakeDbSet<T> and override Find");
}
public T Add(T item)
{
_data.Add(item);
return item;
}
public T Remove(T item)
{
_data.Remove(item);
return item;
}
public T Attach(T item)
{
_data.Add(item);
return item;
}
public void Detach(T item)
{
_data.Remove(item);
}
Type IQueryable.ElementType
{
get { return _query.ElementType; }
}
Expression IQueryable.Expression
{
get { return _query.Expression; }
}
IQueryProvider IQueryable.Provider
{
get { return _query.Provider; }
}
IEnumerator IEnumerable.GetEnumerator()
{
return _data.GetEnumerator();
}
IEnumerator<T> IEnumerable<T>.GetEnumerator()
{
return _data.GetEnumerator();
}
public TDerivedEntity Create<TDerivedEntity>() where TDerivedEntity : class, T
{
return Activator.CreateInstance<TDerivedEntity>();
}
public T Create()
{
return Activator.CreateInstance<T>();
}
public ObservableCollection<T> Local
{
get
{
return new ObservableCollection<T>(_data);
}
}