I am new at Entity Framework Code first and I am building a small app to get used to it.When the site runs for the first time I access existing catalog values inside the database and display this in a drop down using razor.
public void GetCats()
{
using (context = new RecipeContext())
{
try
{
var query = (from r in context.Catalogues
select r).Distinct().ToList();
catalogues = query.Select(t => t.CatalogueName.ToString()).ToList();
catalogues.Sort();
}
catch (Exception exe)
{
labMessage = exe.Message;
}
}
}
Now when I try to add Catalogue values to the context I get the above error.
public void AddCatalogue(string catalogueName)
{
using(context = new RecipeContext())
{
try
{
catalogueName = catalogueName.ToLower();
var catalogue = new RecipeCatalogue { CatalogueName = catalogueName };
if (context.Catalogues.Where(t => t.CatalogueName == catalogueName).Count() > 0)
{
labMessage = "The value already exists";
CatalogueNameAdded = false;
return;
}
context.Catalogues.Add(catalogue);
context.SaveChanges();
catalogueNameAdded = true;
labMessage = "a new catalogue record was added";
}
catch (Exception exe)
{
catalogueNameAdded = false;
labMessage = exe.Message;
}
}
}
The values are being added to the database however but still get the above exception.
Advice perhaps as to why I get this error. This is my Controller method which calls the above method.
[HttpPost]
public JsonResult AddNewCatalogue(string catalogueName)
{
ViewModel model = new ViewModel();
model.AddCatalogue(catalogueName);
return Json(new { ViewModel = model });
}
Is context a field in your model?
I think you shouldn't assign to a field in a using statement. At the closing brace of the using context will be disposed. If you access that field in another place (without re-assigning) you are accessing a disposed object that might raise the exception you are getting.
Try changing your using statetments like this using (var context = new RecipeContext()).
(note var before context) and drop the field.
Your context is being disposed when the using block where you're performing your query is exited. That's the whole point of the using statement:
using(context = new RecipeContext()) {
// ...
}
// context has been disposed at this point
Instead of a using statement, give your class a field to hold a reference to it.
private RecipeContext _context;
public void GetCats() {
_context = new RecipeContext();
// ...
}
public void AddCatalogue(string catalogueName) {
// Use _context here
}
Just make sure that at some point, you call _context.Dispose(). Also, it's probably better to create the context in the constructor or someplace else that's only called once, prior to performing any operations with it.
Just my 2 cents:
The above answers are correct! If you're using some pattern like a repository, I sugest to implement it as a singleton! This way your objects will not be detached, and you're context will not be disposed!
Related
In my method below which is written using c# in asp.net core, I am getting error when executing any of the below update statements. What is the issue with using await SaveContextAsync(); I have noticed I dont get error when only using SaveContext();
The error that I am getting is as follows
Cannot access a disposed object. A common cause of this error is disposing a context that was resolved from dependency injection
and then later trying to use the same context instance elsewhere in your application. This may occur if you are calling Dispose()
on the context, or wrapping the context in a using statement. If you are using dependency injection, you should let the dependency
injection container take care of disposing context instances.
Object name: 'FXDB1Context'.
I am not sure why I am getting this error.
public async Task<IdentityResult> ApproveUserChangeRequest(UserChangeRequest userChangeRequest, string approvedByAuthUserName, string authApplicationName)
{
var userChangeRequestRepository = UserChangeRequestRepository.GetAllAsList();
var userChangeRequestApprovalRepository = UserChangeRequestApprovalRepository.GetAllAsList();
var appSettingRepository = AppSettingRepository.GetAllAsList();
var clientCompanyContactRepository = ClientCompanyContactRepository.GetAllAsList();
var applicationUserRepo = ApplicationUserRepo.GetAllAsList();
int approvedByAuthUserID = GetApprovedByUserId(authApplicationName, approvedByAuthUserName);
// Check if UserChangeRequest is still Pending
bool isUserChangeRequestPending = userChangeRequestRepository.Any(x => x.Id == userChangeRequest.Id && x.ChangeStatus == "Pending");
if (isUserChangeRequestPending && approvedByAuthUserID > 0)
{
// Inserting record in the UserChangeRequestApproval table
InsertUserChangeRequestApproval(userChangeRequest);
await SaveContextAsync();
using (var userTransaction = Context.Database.BeginTransaction())
{
using (var securityTransaction = _securityContext.Database.BeginTransaction())
{
try
{
//Get the Number of approval required for Internal and External Users
int? internalApprovalsRequired = GetApprovals("InternalUserChangeRequestApprovalsRequired", appSettingRepository);
int? externalApprovalsRequired = GetApprovals("ExternalUserChangeRequestApprovalsRequired", appSettingRepository);
//Get the name of the application the auth user belongs to
var authUserApplicationName = GetApplicationName(userChangeRequest.AuthUserId);
//Get the Number of approvals for the request
var numberOfAprovals = userChangeRequestApprovalRepository.Where(x => x.UserChangeRequestId == userChangeRequest.Id).Count();
//If the number of approvals is equal or greater than the Approvals required then Update AppUser or Contact details
if ((authUserApplicationName == "ArgentexTrader" && numberOfAprovals >= internalApprovalsRequired) || (authUserApplicationName == "ArgentexClient" && numberOfAprovals >= externalApprovalsRequired))
{
//Updating the clientcontact table
UpdateClientContact(userChangeRequest, clientCompanyContactRepository);
//Updating the auth user table
UpdateAuthUser(userChangeRequest);
//Updating the IdentityDB user table
UpdateIdentityDBUser(userChangeRequest, applicationUserRepo);
//Updating the UserChangeRequest table
userChangeRequest.ChangeStatus = "Approved";
UserChangeRequestRepository.Update(userChangeRequest);
await SaveContextAsync();
userTransaction.Commit();
securityTransaction.Commit();
return IdentityResult.Success;
}
}
catch (Exception ex)
{
userTransaction.Rollback();
securityTransaction.Rollback();
_logger.Error(ex);
return IdentityResult.Failed(new IdentityError { Description = ex.Message });
}
}
}
}
return null;
}
The error says that a resolved context is been trying to made Disposable.
For More Information: Using Statements in C#
using statement is a scope only process, so this error means that your program tries to use the same instances of "context" in somewhere else, which it cant use it, because as I mentioned it is a "scope only" process.
In your example:
using (var userTransaction = Context.Database.BeginTransaction())
{
using (var securityTransaction = _securityContext.Database.BeginTransaction())
{
}
}
You can make it simple and dont use a using scope or you can be sure that, the context is just used in those using scopes.
i tried this method that I created but it prompts me an error:
Realms.RealmInvalidObjectException:This object is detached. Was it deleted from the realm?'
public void deleteFromDatabase(List<CashDenomination> denom_list)
{
using (var transaction = Realm.GetInstance(config).BeginWrite())
{
Realm.GetInstance(config).Remove(denom_list[0]);
transaction.Commit();
}
}
what is the proper coding for deleting records from database in realm in C# type of coding?
You are doing it the right way. The error message you are getting indicates that the object was removed already. Are you sure it still exists in the realm?
UPDATE:
I decided to update this answer because my comment on the other answer was a bit hard to read.
Your original code should work fine. However, if you want deleteFromDatabase to accept lists with CashDenomination instances that either have been removed already or perhaps were never added to the realm, you would need to add a check. Furthermore, note that you should hold on to your Realm instance and use it in the transaction you created. In most cases, you want to keep it around even longer, though there is little overhead to obtaining it via GetInstance.
public void deleteFromDatabase(List<CashDenomination> denom_list)
{
if (!denom_list[0].IsValid) // If this object is not in the realm, do nothing.
return;
var realm = Realm.GetInstance(config);
using (var transaction = realm.BeginWrite())
{
realm.Remove(denom_list[0]);
transaction.Commit();
}
}
Now, if you want to use identifiers, you could look it up like you do, but still just use Remove:
public void deleteFromDatabase(int denom_id)
{
var realm = Realm.GetInstance(config);
var denom = realm.All<CashDenomination>().FirstOrDefault(c => c.denom_id == denom_id);
if (denom == null) // If no entry with this id exists, do nothing.
return;
using (var transaction = realm.BeginWrite())
{
realm.Remove(denom);
transaction.Commit();
}
}
Finally, if your CashDenomination has denom_id marked as PrimaryKey, you could look it up like this:
public void deleteFromDatabase(int denom_id)
{
var realm = Realm.GetInstance(config);
var denom = realm.ObjectForPrimaryKey<CashDenomination>(denom_id);
if (denom == null) // If no entry with this id exists, do nothing.
return;
using (var transaction = realm.BeginWrite())
{
realm.Remove(denom);
transaction.Commit();
}
}
public void deleteFromDatabase(Realm realm, long cashDenominatorId)
{
realm.Write(() =>
{
var cashDenominator = realm.All<Person>().Where(c => c.Id == cashDenominatorId);
Realm.RemoveRange<CashDenomination>(((RealmResults<CashDenomination>)cashDenominator));
});
}
Which you would call as
Realm realm = Realm.GetInstance(config);
var denom_list = ...
// ...
deleteFromDatabase(realm, denom_list[0].id);
I already made it having this code :) thanks to #EpicPandaForce 's answer.
public void deleteFromDatabase(int denom_ID, int form_ID)
{
//Realm realm;
//and
//RealmConfiguration config = new RealmConfiguration(dbPath, true);
//was initialized at the top of my class
realm = Realm.GetInstance(config);
realm.Write(() =>
{
var cashflow_denom = realm.All<CashDenomination>().Where(c => c.denom_id == denom_ID);
var cashflow_form = realm.All<CashForm>().Where(c => c.form_id == form_ID);
realm.RemoveRange(((RealmResults<CashDenomination>)cashflow_denom));
realm.RemoveRange(((RealmResults<CashForm>)cashflow_form));
});
}
it is now deleting my data without exception :)
Ok here is the deal. using my Model to raise the Child_Update() Method. I know it is not good but im just learing right now. Now i given my Business class as Parameter to Change the already given rows.
It's doin everything fine without any error Messages and there is also no null variable but it's not changing anything in the database.
here i'm using the selectedIndex to choose the right items to update
public void ExecuteAngestellte(object obj)
{
try
{
_selectedIndex.Child_Update(new Farbe { FarbauswahlNr = SelectedIndex.FarbauswahlNr, Kurztext = SelectedIndex.Kurztext, Ressource = SelectedIndex.Ressource, Vari1 = SelectedIndex.Vari1, Vari2 = SelectedIndex.Vari2 });
}
catch (Exception e)
{
MessageBox.Show(e.ToString());
}
}
and here's the child update
public void Child_Update(Farbe data)
{
using (var ctx =Csla.Data.ObjectContextManager<TestDBEntities>.GetManager(EntitiesDatabase.Name))
{
var objectStateManager = ctx.ObjectContext.ObjectStateManager;
var _data = new Datenbank.Farbe();
_data.FarbauswahlNr = data.FarbauswahlNr;
_data.Kurztext = data.Kurztext;
_data.Ressource = data.Ressource;
_data.Var1 = data.Vari1;
_data.Vari2 = data.Vari2;
ctx.ObjectContext.SaveChanges();
}
}
thx for help
as far as I can tell, your _data is not part of the datacontext
I am not sure what the variables all mean so here is a simple update I use for a single record with entity framework
public void UpdateTable(int idRecord, YourContext Context)
{
MyRecord = Context.MyTable.Find(idRecord);
myRecord.Column = "New Value";
Context.SaveChanges();
}
so I think you need to do:
var MyData = ctx.ObjectContext.TableName.Find(id)
I am assuming you are using entity framework. Does this help?
I have a silverlight mvvm with ria project. I have a UI in which admin users can enter info to create new work orders. However, I am having trouble calling the db and adding a new record to the table. I have no code-behind for the UI, the controls are tied to the model through Commands and Command Parameters. So when a user clicks, 'Add new job' it comes here,
public class EditJobViewModel : ViewModelBase
{
private Job _job;
public Job CurrentJob
{
get { return _job; }
set
{
_job = value;
OnPropertyChanged("CurrentJob");
}
}
public ICommand NewJob
{
get
{
return new DelegateCommand(BeginNewJob, (o) => true);
}
}
public void BeginNewJob(object o)
{
_job = new Job();
//_job.JobNumber = _job.JobID.ToString();
_job.AssignedTo = App.userID;
_job.AddedBy = App.userID;
_job.FileTypeJob = "PDF";
_job.AddedTS = DateTime.Now;
_job.OpenDate = DateTime.Now;
BeginSave(o);
}
}
Where Im having trouble is creating a new record in the 'Job' table. On my breakpoint it returns all the columns it needs to, just not a new 'JobID' which is my primary key. This is how I was supposedly trying to create a new record.
public void BeginSave(object o)
{
if (!IsDesignTime)
{
try
{
if (CurrentJob.EntityState == EntityState.New)
{
CurrentJob.AddedBy = App.userID;
CurrentJob.AddedTS = DateTime.Now;
}
CurrentJob.UpdatedBy = App.userID;
CurrentJob.UpdatedTS = DateTime.Now;
// This is here because of a bug in infragistics grid/Entity Framework
foreach (JobFileType ft in CurrentJob.JobFileTypes)
{
if (ft.EntityState != EntityState.Unmodified)
(ft as IEditableObject).EndEdit();
}
foreach (JobTag tag in CurrentJob.JobTags)
{
if (tag.EntityState != EntityState.Unmodified)
(tag as IEditableObject).EndEdit();
}
//(CurrentJob as IEditableObject).EndEdit();
SubmitOperation s = _context.SubmitChanges();
if (s.HasError)
{ }
}
catch (Exception ex)
{ }
}
}
Except that it never hits the EntityState.new. That's just the way I thought to try it. Im thinking there a way to do it from the 'BeginNewJob' command but unable to find a way to create a new JobID or record in general. The Database already has 10000 records and has multiple users creating jobs, so I need a way to get the last job created (getMaxID()??) and increment appropriately, creating a new job on the spot.
İf you use guid type for id column, you will not need to find next id and this approach will decouple new objects from previous objects.
i'm facing a issue while testing the DAL Library which uses LINQ to SQL
Method that is being Tested as below (a simple one):
public List<tblAccount> GetAccountsByCustomer(tblCustomer customer)
{
using (OnlineBankingDataClassesDataContext dbcntx = new OnlineBankingDataClassesDataContext())
{
var accounts = dbcntx.tblAccounts.Where(p => p.tblCustomer.ID.CompareTo(customer.ID)==0);
return accounts.ToList<tblAccount>();
}
}
Test code is as below:
static tblCustomer GetTopOneCustomer()
{
OnlineBankingDataClassesDataContext dbcntx = new OnlineBankingDataClassesDataContext();
var customers = dbcntx.tblCustomers.Take(1);
return customers.Single<tblCustomer>();
}
public static void Should_List_All_Account_By_Customer()
{
tblCustomer customer = GetTopOneCustomer();
DataController dc = new DataController();
List<tblAccount> accounts=dc.GetAccountsByCustomer(customer);
foreach (tblAccount account in accounts)
{
string accountdetails=string.Format("Account ID:{0} \n Account Type:{1} \n Balance:{2} \n BranchName:{3} \n AccountNumber:{4}",
account.ID.ToString(), account.tblAccountType.Name,
account.Balance.ToString(),
account.tblBranch.Name, account.Number);
Console.WriteLine(accountdetails);
}
}
I'm getting an error "Cannot access a disposed object." when accessing associated object like in this case, I'm using account.tblAccountType.Name. I know it has something to do with DataContext. How shall I get this code working.
dbcntx is a disposable object. The Garbage Collector can come along at any time after GetTopOneCustomer() has been called and dispose of it. Which is what looks like is happening.
Try changing GetTopOneCustomer() to:
static tblCustomer GetTopOneCustomer(OnlineBankingDataClassesDataContext dataContext)
{
//Stuff
}
Then inside Should_List_All_Account_By_Customer() change it like so:
using (OnlineBankingDataClassesDataContext dataContext = new OnlineBankingDataClassesDataContext())
{
tblCustomer customer = GetTopOneCustomer(dataContext);
//More Stuff
}
This way you control the lifetime of the dataContext.
Since the the DataContext is in a using statement, using (OnlineBankingDataClassesDataContext dbcntx = new OnlineBankingDataClassesDataContext())
Disposed will be called on it as soon as the context goes out of scope. This results in all entities beeing detached and all actions on the entity that requires a DataContext will fail.
This is what happens when account.Balance.ToString() is called.
One way to solve this is by creating a new context and use context.Attach(entity).