Attaching entities to data contexts - c#

In LINQ to SQL, is it possible to check to see if an entity is already part of the data context before trying to attach it?
A little context if it helps...
I have this code in my global.asax as a helper method. Normally, between requests, this isn't a problem. But right after signing in, this is getting called more than once, and the second time I end up trying to attach the Member object in the same unit of work where it was created.
private void CheckCurrentUser()
{
if (!HttpContext.Current.User.Identity.IsAuthenticated)
{
AppHelper.CurrentMember = null;
return;
}
IUserService userService = new UserService();
if (AppHelper.CurrentMember != null)
userService.AttachExisting(AppHelper.CurrentMember);
else
AppHelper.CurrentMember = userService.GetMember(
HttpContext.Current.User.Identity.Name,
AppHelper.CurrentLocation);
}

I believe there are two methods to do this.
DataContext.TableName.Contains(Item)
or we use the id field. If the item is inserted in the Database, then it will be assigned a row.
if(Item.id == 0)
DataContext.Insert(Item)
else
DataContext.Update(Item)

Rather than attaching to a new data context why not just requery the object in the new datacontext? It believe it is a more reliable and stateless strategy.

Related

Entity Update Issue | C# Entity Framework

I have landed up in a situation here.
I am loading the User from a custom function here :
public User GetUserById(int Id)
{
var User = DBContext.Users.SingleOrDefault(x=>x.Id == Id);
return User;
}
The problem is in the controller where I call this!
var User = GetUserById(Id);
User.Language = UserModel.Language;
//UpdateModel(User); //I tried this but not working.
DBContext.SaveChanges();
The database is not being updated.
I tried loading the User in the controller directly with linq and things go fine.
But, Why is it not working the other way?
Is there any workaround to make it work with this function?
Isn't there any function like DBContext.Users.Update(User). I remember using something similar, but am not able to recollect!
As EBrown said, they need to be the same instance of DbContext. I'm betting your service uses one context and the controller another. So now when it gets to the controller it is disconnected and not tracked by EF.
The solution is to reconnect it to the context used by the controller (there are other ways to achieve this as well).
var User = GetUserById(Id); // returns a disconnected user
User.Language = UserModel.Language;
// Attach back to context and tell EF it is updated
DBContext.Users.Attach(User);
DBContext.Entity(User).State=EntityState.Modified;
DBContext.SaveChanges();
If this is your postback code, you could just as well write aUserUpdate function:
public void UpdateUser(UserModel userViewModel)
{
var userEntity = DBContext.Users.Find(userViewModel.Id); // Get your user from database
Mapper.Map(userViewModel, userEntity); // Use Automapper to move the changed fields into your entity
DbContext.SaveChanges();
}
Then your controller POST is simply:
if (ModelState.IsValid)
{
UpdateUser(UserModel);
// redirect to list or where ever...
}

Generic Create or Update method for CRM 2016 Early bound entities

I've got this method I'm trying to create for CRM.
internal Guid CreateOrUpdateRecord(Entity entity)
{
var guid = Guid.Empty;
if (entity.Id == null || entity.Id == Guid.Empty)
{
guid = _serviceProxy.Create(entity);
}
else
{
_XRM.UpdateObject(entity);
_XRM.SaveChanges();
//_serviceProxy.Update(entity);
guid = entity.Id;
}
return guid;
}
The purpose of it being that I dont need to care if an object is new or gotten from CRM so that my code can just set the variables and throw it in this method to save or update it. With this I don't need to create if structures in multiple places to deal with this issue every time.. I'm using this for multiple entity types.
The code is however giving me some grief in the update method.
This code
_XRM.UpdateObject(entity);
_XRM.SaveChanges()
has a tendency to throw:
The context is not currently tracking the 'xxx' entity.
and this
_serviceContext.Update(entity);
throws:
EntityState must be set to null, Created (for Create message) or
Changed (for Update message) CRM C#
So, any suggestions as to how I should create a single method I can throw any Entity into and it will get updated or created accordingly.
Update
changed the update portion of the method to:
{
if(_XRM.IsAttached(entity) == false)
{
_XRM.Attach(entity);
}
_XRM.UpdateObject(entity);
_XRM.SaveChanges();
guid = entity.Id;
}
Not sure if this is the best way, but it seems to work.
I believe just creating an entity does not add it, which is why you have to attach it. This method is a rather dangerous method in that it doesn't allow for Alternate Keys in update. In that case, the entity will not have an Id, but should have the appropriate attributes that define the alternate key used for the update.

Passing Entity Framework object to helper method for update

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();
}

Context message for UPDATE is not working

I am working on a CRM Dynamics Plugin. There is a field on custom entity named "email". I want to make sure that for two entity records email addresses should be unique. For that purpose I have written following code:
public class Class1 : IPlugin
{
public void Execute(IServiceProvider serviceProvider)
{
// Obtain the execution context from the service provider.
Microsoft.Xrm.Sdk.IPluginExecutionContext context = (Microsoft.Xrm.Sdk.IPluginExecutionContext)
serviceProvider.GetService(typeof(Microsoft.Xrm.Sdk.IPluginExecutionContext));
// Get a reference to the organization service.
IOrganizationServiceFactory factory =
(IOrganizationServiceFactory)serviceProvider.GetService(typeof(IOrganizationServiceFactory));
IOrganizationService service = factory.CreateOrganizationService(context.UserId);
// The InputParameters collection contains all the data passed in the message request.
if (context.InputParameters.Contains("Target") &&
context.InputParameters["Target"] is Entity)
{
Entity entity = (Entity)context.InputParameters["Target"];
//</snippetAccountNumberPlugin2>
// Verify that the target entity represents an account.
// If not, this plug-in was not registered correctly.
if (context.MessageName.ToUpper() == "CREATE")
{
if (entity.LogicalName == "new_assignment1entity")
{
try
{
QueryExpression query = new QueryExpression("new_assignment1entity");
query.ColumnSet.AddColumns("new_email");
EntityCollection result1 = service.RetrieveMultiple(query);
foreach (var a in result1.Entities)
{
int size = result1.Entities.Count;
if (a.Attributes["new_email"].ToString().Equals(entity["new_email"]))
throw new InvalidPluginExecutionException("Duplicate Email found!");
}
}
catch (FaultException<Microsoft.Xrm.Sdk.OrganizationServiceFault>)
{
//You can handle an exception here or pass it back to the calling method.
throw new InvalidPluginExecutionException("Some problem occurred while Querying Records!");
}
}
}
else if (context.MessageName.ToUpper() == "UPDATE")
{
if (entity.LogicalName == "new_assignment1entity")
{
try
{
QueryExpression query = new QueryExpression("new_assignment1entity");
query.ColumnSet.AddColumns("new_email");
EntityCollection result1 = service.RetrieveMultiple(query);
foreach (var a in result1.Entities)
{
int size = result1.Entities.Count;
if (a.Attributes["new_email"].ToString().Equals(entity["new_email"]))
throw new InvalidPluginExecutionException("Duplicate Email found!");
}
}
catch (FaultException<Microsoft.Xrm.Sdk.OrganizationServiceFault>)
{
//You can handle an exception here or pass it back to the calling method.
throw new InvalidPluginExecutionException("Some problem occurred while Querying Records!");
}
}
}
}
}
}
When User creates a new entity record with duplicate email address this code works and shows a dialog box printing error message. But when User edit an existing record (update and existing record) and makes the email address duplicate then this code does not work and updated record with duplicated email address saved.
I am guessing that Context message with UPDATE else part is not working.
Please help me out.
It's not really worth trying to debug this as unfortunately you are going about this in a horribly inefficient way. (Though the most likely cause is the way you are querying being subject to a "feature" of CRM which means you are not querying all the records you think you are).
In short, your code says:
Get me ALL(*) instances of the new_assignment1entity entity
Look at each record until I find one with an email address that matches (case-sensitive) the value just provided in the update
Throw an exception when you encounter the first exact match (otherwise continue with the transaction)
Mains points of note:
QueryExpression will only return the maximum first 5000 records in CRM
You should be filtering your query to only return new_assignment1entity records where the new_email attribute matches the provided value
String.Equals(string) is case-sensitive so to truly check for a duplicate, you should convert the case of each value
Your size variable serves no purpose
Your code will throw an exception if the new/updated record has no value for new_email. You should check that the attribute exists before attempting to access it
I resolved this issue. The problem why only Create execution flow was running and not Update is that I had only registered the plugin for create message step. To overcome this issue, I added a new step in same plugin and registered it with update message as show in following screenshot:
And it worked like charm.
Apart from this, #GregOwens mentioned very helpful points.These should follow as best practices in CRM Development.

Linq2Sql: Manage DataContext

In the following code doesn't work as
public void Foo()
{
CompanyDataContext db = new CompanyDataContext();
Client client = (select c from db.Clients ....).Single();
Bar(client);
}
public void Bar(Client client)
{
CompanyDataContext db = new CompanyDataContext();
db.Client.Attach(client);
client.SomeValue = "foo";
db.SubmitChanges();
}
This doens't work, I get error msg. "An attempt has been made to Attach or Add an entity that is not new, perhaps having been loaded from another DataContext. This is not supported."
How do you work with DataContexts throughout an application so you don't need to pass around a reference?
What
They really mean it with 'This is not supported.'. Attaching to an object fetched from another data context is not implemented.
There are a number of workarounds to the problem, the recommended way is by serializing objects, however this is not easy nor a clean approach.
The most simple approach I found is to use a readonly DataContext for fetching objects like this:
MyDataContext dataContext = new MyDataContext()
{
DeferredLoadingEnabled = false,
ObjectTrackingEnabled = false
};
The objects obtained from this context can be attached to another context but only applies to some scenarios.
The PLINQO framework generates detach for all entities making it easy to detach and reattach objects without receiving that error.
public void Foo()
{
CompanyDataContext db = new CompanyDataContext();
Client client = (select c from db.Clients ....).Single();
// makes it possible to call detach here
client.Detach();
Bar(client);
}
public void Bar(Client client)
{
CompanyDataContext db = new CompanyDataContext();
db.Client.Attach(client);
client.SomeValue = "foo";
db.SubmitChanges();
}
Here is the article that describing how the detach was implemented.
http://www.codeproject.com/KB/linq/linq-to-sql-detach.aspx
Yep. That's how it works.
You have tagged this asp.net so I guess it's a web app. Maybe you want one datacontext per request?
http://blogs.vertigo.com/personal/keithc/Blog/archive/2007/06/28/linq-to-sql-and-the-quote-request-scoped-datacontext-quote-pattern.aspx
(P.S. It's a lot harder in WinForms!)
I've created data access classes that encapsulate all the communication with Linq2Sql.
These classes have their own datacontext that they use on their objects.
public class ClientDataLogic
{
private DataContext _db = new DataContext();
public Client GetClient(int id)
{
return _db.Clients.SingleOrDefault(c => c.Id == id);
}
public void SaveClient(Client c)
{
if (ChangeSetOnlyIncludesClient(c))
_db.SubmitChanges();
}
}
Ofcourse you will need to keep this object instantiated as long as you need the objects.
Checking if only the rigth object has been changed is altso somewhat bothersom, you could make methods like
void ChangeClientValue(int clientId, int value);
but that can become a lot of code.
Attaching and detaching is a somewhat missing feature from Linq2Sql, if you need to use that a lot, you sould probably use Linq2Entities.
I took a look at this and found that it appears to work fine as long as the original DataContext has been disposed.
Try wrapping the DataContext with using() and make sure your changes occur after you've attached to the second DataContext? It worked for me..
public static void CreateEntity()
{
User user = null;
using (DataClassesDataContext dc = new DataClassesDataContext())
{
user = (from u in dc.Users
select u).FirstOrDefault();
}
UpdateObject(user);
}
public static void UpdateObject(User user)
{
using (DataClassesDataContext dc = new DataClassesDataContext())
{
dc.Users.Attach(user);
user.LastName = "Test B";
dc.SubmitChanges();
}
}
You need to handle object versioning.
An entity can only be attached as modified without original state if it declares a version member or does not have an update check policy.
So, if there's no timestamp member or other 'versioning' mechanism provided there's no way for LINQ to determine whether that data has changed - hence the error you are seeing.
I resolved this issue by adding a timestamp column to my tables but there are other ways around it. Rick Strahl has written some decent articles about exactly this issue.
Also, see this and this for a bit more info.

Categories

Resources