Is it possible to get the class that called the SaveChanges() method in the EventHandler?
That's because I have an entity called Activity which can have it's status changed by some parts of the system and I need to log it and save in the database. In the log table I need to store the IDs of the entity that was updated or created and thus caused the activity status to change.
I think I can either do it or try the unmaintainable solution.
The unmaintainable solution would be to add some code to every part of the system that changes the activity status.
PS: I can't use database triggers..
I don't think trying to update another table as part of the SaveChanges is the correct approach here, you would be coupling your logging mechanism to that particular context - what if you wanted to disable logging or switch it out to use a different type of logging? i.e. local file.
I would update the log table along with the entity itself if the update was successful i.e.
var entity = ...
// update entity
if (context.SaveChanges() != 0)
{
// update log table
}
It's possible (but I would recommend against it) using the StackTrace, eg:
public class Test
{
public event EventHandler AnEvent;
public Test()
{
AnEvent += WhoDoneIt;
}
public void Trigger()
{
if (AnEvent != null)
AnEvent(this, EventArgs.Empty);
}
public void WhoDoneIt(object sender, EventArgs eventArgs)
{
var stack = new StackTrace();
for (var i = 0; i < stack.FrameCount; i++)
{
var frame = stack.GetFrame(i);
var method = frame.GetMethod();
Console.WriteLine("{0}:{1}.{2}", i, method.DeclaringType.FullName, method.Name);
}
}
}
public class Program
{
static void Main(string[] args)
{
var test = new Test();
test.Trigger();
Console.ReadLine();
}
}
If you look at the output of the program you can figure out which stack frame you want to look at and analyze the caller based on the Method of that frame.
HOWEVER, this can have serious performance implications - the stack trace is quite an expensive object to create, so I would really recommend changing your code to keep track of the caller in a different way - one idea could be to store the caller in a threadstatic variable before calling SaveChanges and then clearing it out afterwards
From your post it sounds like you're more interested in which entities are updating rather than which method called SaveChanges.
If that's the case, you can examine the pending changes and see which entities are either added or modified (or deleted if you care) and do your logging based on that information.
You would do that like this:
public override int SaveChanges()
{
if (changeSet != null)
foreach (var dbEntityEntry in ChangeTracker.Entries())
{
switch (dbEntityEntry.State)
{
case EntityState.Added:
// log your data
break;
case EntityState.Modified:
// log your data
break;
}
}
return base.SaveChanges();
}
Related
I'm on a team using an EF, Code-first approach with ODP.Net (Oracle). We need to attempt to write updates to multiple rows in a table, and store any exceptions in a collection to be bubbled up to a handler (so writing doesn't halt because one record can't be written). However, this code throws an exception saying
System.InvalidOperationException: The operation cannot be completed because the DbContext has been disposed.
I'm not sure why. The same behavior occurs if the method is changed to be a synchronous method and uses .Find().
InvModel _model;
public InvoiceRepository(InvModel model)
{
_model = model;
}
public void SetStatusesToSent(IEnumerable<Invoice> Invoices)
{
var exceptions = new List<Exception>();
foreach (var id in invoices)
{
try
{
var iDL = await _model.INVOICES.FindAsync(id);/*THROWS A DBCONTEXT EXCEPTION HERE*/
iDL.STATUS = Statuses.Sent; // get value from Statuses and assign
_model.SaveChanges(); //save changes to the model
}
catch (Exception ex)
{
exceptions.Add(ex);
continue; //not necessary but makes the intent more legible
}
}
}
Additional detail update: _model is injected by DI.
Remember that LINQ executes lazily - that is when you actually use the information.
The problem might be, that Your DbContext has gone out of scope...
Use .ToList() or .ToArray() to force execution at that time.
I have a simple functional style test for output of a command that I've written using Mediatr's IRequest and IRequestHandler<>
[Fact]
public void TestReturnValuesAsync()
{
// Arrange
var handler = new Mock<IRequestHandler<SyncSubmerchantDataCommand, CommandResult<int>>>();
handler.Setup(x => x.Handle(It.IsAny<SyncSubmerchantDataCommand>(), It.IsAny<CancellationToken>())).ReturnsAsync(new CommandResult<int>(0, ResultStatus.Success, "string"));
// Act
var result = handler.Object.Handle(new SyncSubmerchantDataCommand(), new CancellationToken());
// Assert
result.Result.Data.ShouldBe(0);
result.Result.Status.ShouldBe(ResultStatus.Success);
result.Result.Message.ShouldBe("string");
}
Since this command runs as a background task, I don't want it interrupted. I have a variable, submerchantList, that is of type List<T> which is used in a foreach loop to do work. The work is set in a try-catch because I don't want the command interrupted, as I stated before. I want to test the output of the what is written to my logs (_log.info) if an exception is thrown during this process.
public class CommandNameHandler : IRequestHandler<source, destination> {
// constructors and privates
public async destination Handle(param, token)
{
var submerchantList = db call.ToList();
foreach (var item in submerchantList)
{
try {
//does work
}
catch (Exception e) {
if (item != null)
_log.info($"{e} - {item.Id}");
}
return some out put
}
The problem is that I can't seem to figure out how to set the value of the any variable, such as the submerchantList within the Handle in order to throw the exception for my next test. I'm stumped.
Any help would be greatly appreciated.
SOLUTION:
Here was the solution: Stubbing the database call by injecting an in-memory DbSet. I used this resource learn.microsoft.com/en-us/ef/ef6/fundamentals/testing/… This issue was db call.ToList It looked something like this _db.Table.Include(x => x.Foreign).Where(x => x.Foreign.Field == Enum.Value).ToListAsync() While I was setting up the Mock DbSet, I had to use the string version, not the LINQ-chain version in the unit test. So, that means mockDbset.Setup(x => x.Table.Include("Foreign")).Returns(myCustomDbSet); Hope that helps someone!
public static void CacheUncachedMessageIDs(List<int> messageIDs)
{
var uncachedRecordIDs = LocalCacheController.GetUncachedRecordIDs<PrivateMessage>(messageIDs);
if (!uncachedRecordIDs.Any()) return;
using (var db = new DBContext())
{
.....
}
}
The above method is repeated regularly throughout the project (except with different generics passed in). I'm looking to avoid repeated usages of the if (!uncachedRecordIDs.Any()) return; lines.
In short, is it possible to make the LocalCacheController.GetUncachedRecordIDs return the CacheUncachedMessageIDs method?
This will guarantee a new data context is not created unless it needs to be (stops accidentally forgetting to add the return line in the parent method).
It is not possible for a nested method to return from parent method.
You can do some unhandled Exception inside GetUncachedRecordIDs, that will do the trick, but it is not supposed to do this, so it creates confusion. Moreover, it is very slow.
Another not suggested mechanic is to use some goto magic. This also generates confusion because goto allows unexpected behaviour in program execution flow.
Your best bet would be to return a Result object with simple bool HasUncachedRecordIDs field and then check it. If it passes, then return. This solution solves the problem of calling a method, which is Any() in this case.
var uncachedRecordIDsResult = LocalCacheController.GetUncachedRecordIDs<PrivateMessage>(messageIDs);
if(uncachedRecordIDsResult.HasUncachedRecordIDs) return;
My reasoning for lack of this feature in the language is that calling GetUncachedRecordIDs in basically any function would unexpectedly end that parent function, without warning. Also, it would intertwine closely both functions, and best programming practices involve loose coupling of classes and methods.
You could pass an Action to your GetUncachedRecordIDs method which you only invoke if you need to. Rough sketch of the idea:
// LocalCacheController
void GetUncachedRecordIDs<T>(List<int> messageIDs, Action<List<int>> action)
{
// ...
if (!cached) {
action(recordIds);
}
}
// ...
public static void CacheUncachedMessageIDs(List<int> messageIDs)
{
LocalCacheController.GetUncachedRecordIDs<PrivateMessage>(messageIDs, uncachedRecordIDs => {
using (var db = new DBContext())
{
// ...
}
});
}
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();
}
I'm dealing with a courious scenario.
I'm using EntityFramework to save (insert/update) into a SQL database in a multithreaded environment. The problem is i need to access database to see whether a register with a particular key has been already created in order to set a field value (executing) or it's new to set a different value (pending). Those registers are identified by a unique guid.
I've solved this problem by setting a lock since i do know entity will not be present in any other process, in other words, i will not have same guid in different processes and it seems to be working fine. It looks something like that:
static readonly object LockableObject = new object();
static void SaveElement(Entity e)
{
lock(LockableObject)
{
Entity e2 = Repository.FindByKey(e);
if (e2 != null)
{
Repository.Insert(e2);
}
else
{
Repository.Update(e2);
}
}
}
But this implies when i have a huge ammount of requests to be saved, they will be queued.
I wonder if there is something like that (please, take it just as an idea):
static void SaveElement(Entity e)
{
(using ThisWouldBeAClassToProtectBasedOnACondition protector = new ThisWouldBeAClassToProtectBasedOnACondition(e => e.UniqueId)
{
Entity e2 = Repository.FindByKey(e);
if (e2 != null)
{
Repository.Insert(e2);
}
else
{
Repository.Update(e2);
}
}
}
The idea would be having a kind of protection that protected based on a condition so each entity e would have its own lock based on e.UniqueId property.
Any idea?
Don't use application-locks where database transactions or constraints are needed.
The use of a lock to prevent duplicate entries in a database is not a good idea. It limits the scalability of your application be forcing only a single instance to ever exist that can add or update such records. Or worse, someone will eventually try to scale the application to multiple processes or servers and it will cause data corruption (since locks are local to a single process).
What you should consider instead is using a combination of unique constraints in the database and transactions to ensure that no two attempts to add the same entry can both succeed. One will succeed - the other will be forced to rollback.
This might work for you, you can just lock on the instance of e:
lock(e)
{
Entity e2 = Repository.FindByKey(e);
if (e2 != null)
{
Repository.Insert(e2);
}
else
{
Repository.Update(e2);
}
}