This documentation explains how you would resolve concurrency conflict when updating the database through the entity framework.
The solution revolves around reading values of the overlapping instances in a prop-value dictionary, deciding how to resolve the overlap, updating the concurrency token, and then saving the results back to the database; repeat until successful. Copy-pasted the code from docs here.
var saved = false;
while (!saved)
{
try
{
// Attempt to save changes to the database
context.SaveChanges();
saved = true;
}
catch (DbUpdateConcurrencyException ex)
{
foreach (var entry in ex.Entries)
{
if (entry.Entity is Person)
{
var proposedValues = entry.CurrentValues;
var databaseValues = entry.GetDatabaseValues();
foreach (var property in proposedValues.Properties)
{
var proposedValue = proposedValues[property];
var databaseValue = databaseValues[property];
// TODO: decide which value should be written to database
// proposedValues[property] = <value to be saved>;
}
// Refresh original values to bypass next concurrency check
entry.OriginalValues.SetValues(databaseValues);
}
else
{
throw new NotSupportedException(
"Don't know how to handle concurrency conflicts for "
+ entry.Metadata.Name);
}
}
}
}
In this example, databaseValues is a prop-value dictionary, not an instance of the object.
In my application, conflicts can be resolved by calling a method on the instance with the original values and proposing an update. I wonder if you can get an instance of the object in the DB (which is expected from an ORM anyway) instead of the prop-value dictionary from ex.Entries (i.e., entry.GetDatabaseValues() and entry.CurrentValues;).
I could think of a method that iterates through the prop-value dictionary and create an instance; though I am wondering if there is any built-in/better solution.
(If relevant, the database is Postgres.)
Related
I am writing a system that has a concept of idempotent operations: If clients give the system an operation id more than once the system will reject those "duplicated" operations immediately.
I want to implement this by storing UUID Primary-Key values in a table in SQL server such that SQL server will just reject duplicated writes, as expected. My problem comes when EF Core tries to be smart about these values and cache them: EF Core will reject the addition of the entity without ever pinging SQL server because it knows there's already a tracked entity with that same PK. This behavior is ideal in most scenarios but in my specific scenario it will become very memory-intensive real quick. I don't want this behavior.
This is the code that I'm using to manually trigger the specific error I need to give clients of the system:
Action throwIdempotentOpError = () => {
throw new ExecutionError("The operation you are trying to perform was already performed, please try again with a new client mutation id");
};
if (opsRepo.IdempotentOperations.Local.Any(op => op.ClientMutationId == mutationGuid)) {
throwIdempotentOpError();
}
var operation = new IdempotentOperation {
ClientMutationId = mutationGuid,
CreatedAt = DateTime.UtcNow,
UpdatedAt = DateTime.UtcNow,
RawDocument = context.Document.OriginalQuery,
Status = IdempotentOperationStatus.Started
};
try {
opsRepo.IdempotentOperations.Add(operation);
await opsRepo.SaveChangesAsync();
} catch (DbUpdateException ex) {
if (ex.InnerException != null && ex.InnerException.Message.StartsWith("Violation of PRIMARY KEY constraint 'PK_IdempotentOperations'")) {
throwIdempotentOpError();
}
throw;
}
Ideally I would only have to throw the error inside the catch block.
How can I disable that entity tracking behavior on the .Add call?
For context: opsRepo is a DbContext
You can solve your problem with cashing added Ids and save them into for example Redis, check new ids with cached Ids and prevent to insert duplicate items and reject them. But for solving problem with DbContext, you should detach the inserted items like this:
...
try {
opsRepo.IdempotentOperations.Add(operation);
await opsRepo.SaveChangesAsync();
//detached inserted entities
ClearDbContextState();
}
...
public void ClearDbContextState()
{
var entities = opsRepo.ChangeTracker.Entries<IdempotentOperations>().Where(e => e.State == EntityState.Added ||
e.State == EntityState.Modified).ToList();
foreach (var entry in entities)
entry.State = EntityState.Detached;
}
I ended up using IHttpContextAccessor as a way to scope out the injection of my DbContext implementation, side-stepping the issue #Panagiotis Kanavos commented.
I'm working with Marten as my data layer and it's been great so far, but I've run into an issue that just doesn't make sense. I have a simple method that saves a transaction (a purchase) then updates a listing, adding the ID of the transaction to a collection. My problem is, it appears that Marten is not storing my updated listing, although it is storing the transaction.
When I look in the database, the TransactionIds property is null, but if I step through the code, everything seems to execute correctly. Am I doing something wrong here?
public async Task CreateListingTransactionAsync(ListingTransaction transaction)
{
if (transaction == null)
throw new ValidationException("Transaction is required to create a transaction");
bool isNew = transaction.Id == Guid.Empty;
await _listingTransactionValidator.ValidateAndThrowAsync(transaction);
using (var session = _store.LightweightSession())
{
session.Store(transaction);
if (isNew)
{
var listing = await session.LoadAsync<Listing>(transaction.ListingId);
if (listing == null)
throw new EntityNotFoundException($"Listing with Id: {transaction.ListingId} not found");
if (listing.TransactionIds == null)
listing.TransactionIds = new List<Guid>();
listing.TransactionIds.Add(transaction.Id);
session.Store(listing);
}
await session.SaveChangesAsync();
}
}
There could be a problem with the serialization of TransactionIds collection.
If that's not the case then here are some random things to try (and try to understand why it worked later):
Try session.Update(listing); instead of session.Store(listing);.
Try different type of document session. http://jasperfx.github.io/marten/documentation/troubleshoot/
I'm using Entity Framework 5 with MySQL Database and just wanted to update a row attribute "user_loginstatus" between 0 and 1. The first time when I log in via client it updates just fine for the first attempt, after trying to update again it doesn't do anything with no exception.
I log in like this:
public async void LoginExecute()
{
// Checking Connection before etc...
if (await _dataService.IsLoginDataValidTask(UserObj.Username, md5))
{
Trace.WriteLine("LoginCommand Execute: Eingeloggt");
UserObj = await _dataService.GetUserDataTask(UserObj.Username);
await _dataService.SetUserStatusTask(UserObj.Id, 1);
await _dataService.WriteLog(UserObj.Id, "login", "Programm", GetLocalAdress());
Messenger.Default.Send(UserObj);
Messenger.Default.Send(new NotificationMessage("GoToMenuPage"));
}
else
{
// Error Stuff...
}
}
SetUserStatus Method in DataService Class
public Task SetUserStatusTask(int id, int status)
{
return Task.Factory.StartNew(() =>
{
try
{
var user = _entities.users.Find(id);
user.user_loginstatus = status;
_entities.SaveChanges();
}
catch (Exception ex)
{
Trace.WriteLine("DataService SetUserStatusTask: " + ex.Message);
}
});
}
GetUserData Method in DataService Class
public Task<User> GetUserDataTask(string username)
{
return Task.Factory.StartNew(() =>
{
try
{
var user = from us in _entities.users
where us.user_name.Equals(username)
select new User
{
Id = us.user_id,
Username = us.user_name,
FirstName = us.user_firstname,
LastName = us.user_lastname,
Gender = us.user_gender,
Email = us.user_mail,
Group = us.user_usergroup,
Avatar = us.user_avatar,
LoginStatus = 1
};
return user.FirstOrDefault();
}
catch (Exception ex)
{
Trace.WriteLine("DataService GetUserDataTask: " + ex);
return null;
}
});
}
So "users" is my table from the database and "User" / "UserObj" my custom Object.
With the Messenger (from MVVM Light) I just set via MainViewModel the Views, reset the unused ViewModels (ViewModel = new VieModel(...); or ViewModel = null;) and pass the current / logged in User Object.
With the same strategy I just Logout like this
public ICommand LogoutCommand
{
get
{
return new RelayCommand(async () =>
{
await _dataService.SetUserStatusTask(CurrentUser.Id, 0);
if(CurrentUser.Id > 0 && IsLoggedIn)
await _dataService.WriteLog(CurrentUser.Id, "logout", "Programm", GetLocalAdress());
IsLoggedIn = false;
CurrentUser = new User();
Messenger.Default.Send(new NotificationMessage("GoToLoginPage"));
});
}
}
So I can log in with my running Client so often I want, but the "user_loginStatus" only sets the changes the first login time to 1 and back to 0, but when I log out then and login back with the same user, it wont change it anymore. When I login (still same running Client) with another user it sets again the first time the "user_loginstatus" to 1 and back to 0 and then only again when I restart my Client..
What could I do wrong?
This is just basically from my comment regarding the original question:
I had similiar problems several times. Usually it is based on the fact that the entity you modified can't be validated properly and your dbContext fails without a proper exception because it still holds on to false entity. If this is the case you could circumvent this problem by using scoped contexts and embedding your data access operations in a using statement.
Alternatively you could try to explicitly tell EF that the entity has changes e.g.:
_entities.Entry(user).State = EntityState.Modified;
Regarding your other question:
In theory you shouldn't have to tell EF explicitly that the entity's values have changed. Change tracking should do that automatically. The only exception i could think of, is when you try to modify an entity that is explicitly not tracked anymore. When you call _entities.Find(id) it will look in the context if it finds the object with the matching primary key value and load it. Since you already modified this object before, the context will simply get the old object you already modified to set the login status the first time.
This "old" object is probably not tracked anymore and you have to tell EF explicitly that it has changed, by changing it's state from attached to modified.
in LoginExecute() you have UserObj, but in LogoutCommand() you have CurrentUser. Is it OK?
I'm new to using entity as a data layer between MVC and SQL Server, so I apologize up front if what I'm doing is bad practice.
Let me start by sharing the code that is handling the update.
Update Delivery:
public bool One(Delivery toUpdate)
{
using (var dbContext = new FDb())
{
try
{
var deliveryInDb = this.dbTable(dbContext).Single(x => x.DeliveryId == toUpdate.DeliveryId);
dbContext.Entry(deliveryInDb).CurrentValues.SetValues(toUpdate);
//removal first
List<DeliveryDay> currentDays = FEngineCore.DeliveryDay.Get.ForValue((x => x.DeliveryId), toUpdate.DeliveryId);
List<DeliveryTime> currentTimes = FEngineCore.DeliveryTime.Get.ForValue((x => x.DeliveryId), toUpdate.DeliveryId);
//remove delivery days that are not needed
foreach (var curDay in currentDays)
{
if (!toUpdate.DeliveryDays.Select(x => x.DeliveryDayId).Contains(curDay.DeliveryDayId))
{
FEngineCore.DeliveryDay.Delete.One((x => x.DeliveryDayId), curDay.DeliveryDayId);
deliveryInDb.DeliveryDays.Remove(curDay);
}
}
//remove delivery times that are not needed
foreach (var curTime in currentTimes)
{
if (!toUpdate.DeliveryTimes.Select(x => x.DeliveryTimeId).Contains(curTime.DeliveryTimeId))
{
FEngineCore.DeliveryTime.Delete.One((x => x.DeliveryTimeId), curTime.DeliveryTimeId);
deliveryInDb.DeliveryTimes.Remove(curTime);
}
}
foreach (var day in toUpdate.DeliveryDays)
{
if (day.DeliveryDayId == 0)
{
dbContext.DeliveryDays.Add(day);
}
else
{
if (dbContext.DeliveryDays.Local.Any(e => e.DeliveryDayId == day.DeliveryDayId))
{
dbContext.Entry(dbContext.DeliveryDays.Local.First(e => e.DeliveryDayId == day.DeliveryDayId)).CurrentValues.SetValues(day);
dbContext.Entry(dbContext.DeliveryDays.Local.First(e => e.DeliveryDayId == day.DeliveryDayId)).State = EntityState.Modified;
}
else
{
DeliveryDay modDay = new DeliveryDay
{
DayOfWeek = day.DayOfWeek,
DeliveryDayId = day.DeliveryDayId,
DeliveryId = day.DeliveryId,
Interval = day.Interval
};
dbContext.DeliveryDays.Attach(modDay);
dbContext.Entry(modDay).State = EntityState.Modified;
}
deliveryInDb.DeliveryDays.Add(day);
}
}
foreach (var time in toUpdate.DeliveryTimes)
{
if (time.DeliveryTimeId == 0)
{
dbContext.DeliveryTimes.Add(time);
}
else
{
if (dbContext.DeliveryTimes.Local.Any(e => e.DeliveryTimeId == time.DeliveryTimeId))
{
dbContext.Entry(dbContext.DeliveryTimes.Local.First(e => e.DeliveryTimeId == time.DeliveryTimeId)).CurrentValues.SetValues(time);
dbContext.Entry(dbContext.DeliveryTimes.Local.First(e => e.DeliveryTimeId == time.DeliveryTimeId)).State = EntityState.Modified;
}
else
{
DeliveryTime modTime = new DeliveryTime
{
DeliveryId = time.DeliveryId,
DeliveryLocationId = time.DeliveryLocationId,
DeliveryTimeId = time.DeliveryTimeId,
DropoffTime = time.DropoffTime
};
dbContext.DeliveryTimes.Attach(modTime);
dbContext.Entry(modTime).State = EntityState.Modified;
}
deliveryInDb.DeliveryTimes.Add(time);
}
}
dbContext.SaveChanges();
dbContext.Entry(deliveryInDb).State = EntityState.Detached;
return true;
}
catch (Exception ex)
{
Console.WriteLine(ex.InnerException);
return false;
}
}
}
Let me continue by explaining that the delivery object has 2 children; DeliveryTime and DeliveryDay. The issue that arises happens when I try to remove one deliveryTime and modify nothing else. The end result of running the code normally (not in debug) is that the deliveryTime is in fact not removed. Here's the interesting thing guys, when I debug it and go through the break points, everything works as expected!
Let me continue by posting the code that is running behind the removal method of the deliveryTime (actually all entity objects in my system).
public bool One<V>(Expression<Func<T, V>> property, V value) where V : IComparable
{
using (var dbContext = new FoodsbyDb())
{
try
{
T toDelete;
//get the body as a property that represents the property of the entity object
MemberExpression entityPropertyExpression = property.Body as MemberExpression;
//get the parameter that is representing the entity object
ParameterExpression entityObjectExpression = (ParameterExpression)entityPropertyExpression.Expression;
//represent the value being checked against as an expression constant
Expression valueAsExpression = Expression.Constant(value);
//check the equality of the property and the value
Expression equalsExpression = Expression.Equal(entityPropertyExpression, valueAsExpression);
//create an expression that takes the entity object as a parameter, and checks the equality using the equalsExpression variable
Expression<Func<T, bool>> filterLambda = Expression.Lambda<Func<T, bool>>(equalsExpression, entityObjectExpression);
toDelete = this.dbTable(dbContext)
.SingleOrDefault(filterLambda);
if (toDelete != null)
{
this.dbTable(dbContext)
.Remove(toDelete);
dbContext.SaveChanges();
return true;
}
return false;
}
catch (Exception ex)
{
Console.WriteLine(ex.InnerException);
return false;
}
}
}
The code above is obviously generic, and it handles all my entity objects. I have tested it in and out and know for sure the problem does not lie in there. I thought it would be helpful to post it so you all can have a full understanding of what's going on.
Here's my best guess as to what's going on:
The reference to the removed deliveryTime still exists when the database context is saved, but when I debug, the system has enough time to remove the context.
Here was one of my attempted solutions:
Remove all references to the children objects immediately after setting currentDays and currentTimes and then proceeding to add them back to deliveryInDb as you enumerate through them.
Because I am new to all of this, if you see some bad practice along with the solution, I wouldn't mind constructive criticism to improve my programming method.
I actually encountered this issue in a project at work. The project is an older MVC4 project using EF 6.1.
In our situation, a simple update attempting to set a related entity property to null was failing to actually set it to null while running the web app normally (in debug mode). When setting a break point on the line of code that sets the property to null the database would be updated as expected, though. So, the update was working when a break point was in place but not working when allowed to run normally.
Using an EF interceptor, we could see that, with the break point in place, the update query was going through as expected.
Now, in our situation the related entity was using the virtual keyword to allow for lazy loading. I think this is the root of the issue. When a break point is present, EF has enough time to both lazily load that related entity and evaluate whatever it needs to evaluate and finally set it to null. When running without a break point, I think EF gets caught up trying to lazily load that entity and therefore fails to think it needs to be updated. To be clear, I was both accessing the related entity property for the first time and setting it null using a one-liner of code.
foo.Bar = null;
I resolved this issue, in our scenario, by accessing that property at least once prior to setting it to null so that EF is forced to load it. With it loaded, setting it to null seems to work as intended now. So again, to be clear, I think the issue is a combo of lazy loading and the one-liner of code both accessing that property for the first time and assigning it to null.
It appears that you're using multiple instances of your DbContext, which are not synchronized.
The solution would be to use a single instance, and pass that instance between your methods.
I'm having some trouble using a helper method to perform an update to a set of model objects. The table uses a lookup table to hold 5 records per agent/user. If I want to save the record for the agent, I need to save that record onto the AgentTransmission table, and up to 5 other records on the RelationshipCodeLookup table.
Since I have to do this five times per agent, and we must do the process in the Create and Edit methods, I created a helper method to save the records. This works fine during the create process as we're simply doing a DbContext.Add(). However when I need to perform an update, I get the error message
An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key.
I think this has to do with the fact I'm passing the model object to my helper method, and therefore the DbContext thinking that it has two separate objects to keep track of. I say this because the lines of code that are commented out work just fine and allow me to save the object. Passing the object to the helper method, however, gets the above error.
Does anyone know of a way around this (using a helper method to perform an update)?
Controller Action
//Save relationship codes in lookup table
if (AgentTransmissionValidator.ValidateRelationshipCode(agenttransmission.RelationshipCode1))
{
//db.Entry(agenttransmission.RelationshipCode1).State = EntityState.Modified;
//db.SaveChanges();
SaveRelationshipCodes(agenttransmission.RelationshipCode1, agenttransmission.ID);
}
if (AgentTransmissionValidator.ValidateRelationshipCode(agenttransmission.RelationshipCode2))
{
//db.Entry(agenttransmission.RelationshipCode1).State = EntityState.Modified;
//db.SaveChanges();
SaveRelationshipCodes(agenttransmission.RelationshipCode2, agenttransmission.ID);
}
if (AgentTransmissionValidator.ValidateRelationshipCode(agenttransmission.RelationshipCode3))
{
//db.Entry(agenttransmission.RelationshipCode1).State = EntityState.Modified;
//db.SaveChanges();
SaveRelationshipCodes(agenttransmission.RelationshipCode3, agenttransmission.ID);
}
if (AgentTransmissionValidator.ValidateRelationshipCode(agenttransmission.RelationshipCode4))
{
//db.Entry(agenttransmission.RelationshipCode1).State = EntityState.Modified;
//db.SaveChanges();
SaveRelationshipCodes(agenttransmission.RelationshipCode4, agenttransmission.ID);
}
if (AgentTransmissionValidator.ValidateRelationshipCode(agenttransmission.RelationshipCode5))
{
//db.Entry(agenttransmission.RelationshipCode1).State = EntityState.Modified;
//db.SaveChanges();
SaveRelationshipCodes(agenttransmission.RelationshipCode5, agenttransmission.ID);
}
Helper Method
public void SaveRelationshipCodes(RelationshipCodeLookup relCode, int id)
{
if (relCode.AgentId == 0) relCode.AgentId = id;
relCode.LastChangeDate = DateTime.Now;
relCode.LastChangeId = Security.GetUserName(User);
//Check to see if record exists and if not add it
if (db.RelationshipCodeLookup.Find(id, relCode.RelCodeOrdinal) != null)
{
db.Entry(relCode).State = EntityState.Detached;
}
else
{
if(relCode.RelCodeOrdinal == 0) relCode.RelCodeOrdinal = FindOrdinal(relCode);
db.RelationshipCodeLookup.Add(relCode);
}
db.SaveChanges();
}
EDIT
After scouring the web I attempted to save via this method
//Check to see if record exists and if not add it
if (db.RelationshipCodeLookup.Find(id, relCode.RelCodeOrdinal) != null)
{
db.Entry(relCode).CurrentValues.SetValues(relCode);
}
else
{
Member 'CurrentValues' cannot be called for the entity of type 'RelationshipCodeLookup because the entity does not exist in the context. To add an entity to the context call the Add or Attach method of DbSet<RelationshipCodeLookup>
However.... doing that only puts me back at the start with the following error on db.RelationshipCodeLookup.Attach(relCode);
An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key.
Try this:
db.RelationshipCodeLookup.Attach(relCode);
db.Entry(relCode).State = EntityState.Modified;
For updates you want to attach the detached object then set it's state to modified.
The issue here seems to be that the Entity Framework cannot track two objects of the same kind at the same time. Because of that I find the solution to this problem more than a little weird. By calling .Find() on the DbContext and instantiating a second copy of the model object I was finally able to save. Seems to break all the rules the EF was laying out for me in the error messages, but hey it works.
public void SaveRelationshipCodes(int id, RelationshipCodeLookup relCode)
{
if (relCode.AgentId == 0) relCode.AgentId = id;
relCode.LastChangeDate = DateTime.Now;
relCode.LastChangeId = Security.GetUserName(User);
//Check to see if record exists and if not add it
if (db.RelationshipCodeLookup.Find(id, relCode.RelCodeOrdinal) != null)
{
//Need to call .Find to get .CurrentValues method call to work
RelationshipCodeLookup dbRelCode = db.RelationshipCodeLookup.Find(id, relCode.RelCodeOrdinal);
db.Entry(dbRelCode).CurrentValues.SetValues(relCode);
}
else
{
if(relCode.RelCodeOrdinal == 0) relCode.RelCodeOrdinal = FindOrdinal(relCode);
db.RelationshipCodeLookup.Add(relCode);
}
db.SaveChanges();
}