I have a web application using EF4. I am somewhat new to EF and now trying to implement change Audit.I tried to do this by trapping the SavingChanges event of the Context Class as below
partial void OnContextCreated()
{
this.SavingChanges += new EventHandler(TicketContainer_SavingChanges);
}
So the event handler accesses the changed records by the following
this.ObjectStateManager.GetObjectStateEntries(
EntityState.Added | EntityState.Modified);
This works fine and I am creating column level audit for selected tables. Every table/entity has an ID field which is an identifier with columnName="ID". So in my audit routine I simply accesses data from column with name "Id" to get the ID of audited record.
The problem I face is during insert . The new record has no ID yet as it is an identity column in the database and is always 0.
One solution I can think of is using GUID for all Ids.But is there a way to implement this using standard int32 Identity Ids?
thanks
When we insert data through EF the identity column is not generted while insertion. To get the Id of Identity columns we have to insert the data first then only we can get the Id of coulmn.
please go through the below which might be helpful to you.
http://www.codeproject.com/KB/database/ImplAudingTrailUsingEFP1.aspx
I don't now how many entities you have but in our own implementation of audit tracking we created a specific audit entity for each entity so we could link them together trough navigational properties and let the database set the identity keys.
If you use inheritance for your audit entities it's quit easy to query them.
Hope this helps :)
Identity columns are not generated while insertion. Once data is inserted then only you can get identity column data in EF. So, you can try some work around by getting Id after insertion and then populating audit table with that Id.
Related
I am trying to insert multiple rows using the following code. SaveChanges() works for the first record but if fails when it tries the next one. My guess is that each time it is trying to insert all records. Not sure if this is correct or not, and if it is correct how can I change the code to make it correct. Following is my code:
Contrroller:
foreach(var m in pms)
{
_pmService.AddPms(m);
}
And in _pmService.AddPms:
_pmRepository.Add(pm);
_pmRepository.SaveChanges();
_pmRepository.Add (actually this is from BaseRepository and pmRepository extends this Base)
_ctx.Set<T>().Add(entity);
Finally, here is my SaveChanges() (again this is also from BaseRepostiroy)
_ctx.ChangeTracker.DetectChanges();
return _ctx.SaveChanges();
So in controller, I am looping through each entry, and then calling Add. The Add in service is calls Add in BaseRepository and then it does the SaveChanges(). For first record it works without any issues but 2nd record onwards it fails. And following is the error:
"Saving or accepting changes failed because more than one entity of type XXXXXXXXXXXXX have the same primary key value. Ensure that explicitly set primary key values are unique. Ensure that database-generated primary keys are configured correctly in the database and in the Entity Framework model. Use the Entity Designer for Database First/Model First configuration. Use the 'HasDatabaseGeneratedOption\" fluent API or 'DatabaseGeneratedAttribute' for Code First configuration."
And I am using DatabaseFirst approach.
I found the answer it is with StoreGeneratedPattern. I had to set this Identity in edmx file for the primary key field and it worked.
StoreGeneratedPattern="Identity"
Asp.net mvc 5 Identity 2.0 will create 5 tables automatically when run the mvc project.
Here, my question is why some tables like AspnetUser, it's item 'Id' type defined to string.
The String seems like GUID, but why it doesn't define to guid type instead of using string.
Is it transfer data type from string or do something when quering data ?
I can't figure out why it define to string, but look like guid ?
another table have same problem like AspnetRole, it's item 'UserId', 'RoleId' defined to string too.
Have any idea ?
I'm guessing this is having different reasons.
One reason is the insert performance for Guids, which will get slower and slower after an amount of data (Clustered indexes).
Another reason is the difference of handling Guid in different databases. Microsoft Sql Server has an UniqueIdentifier type that is a Guid, MySql will store them as strings, Oracle stores the raw bytes of a Guid...
I hope this explains a part of your queustion, as not fully :)...
Identity framework not only created for code first approach to be generate database tables with given fields or datatypes. Identity framework can be used against existing database or migrate old asp.net membership provider, or we can use our own table names with extra database fields to store more data on identity tables.
Further more, the Id of the aspnetUser table (that is the User table) used as string because, we can use Guid, integer, long etc. for this field depending on the requirement.
E.g. : If you decided to use integer as Id of the aspnetUser table (User table), then the database field will be auto increment int (or bigInt or etc.) field. But you need to do model binding in order to fulfill entity framework migration requirements.
By default we get Guid inserted into this field when we use out of the box asp.net Identity framework.
When you have defined roles for the registered user, there will be record added into AspnetRole table, this is also completely depending on the fields we defined on the tables as I discussed before. If we decided to use integer as Id of the aspnetUser table, then AspnetRole table fields updated according to the relationship with aspnetUser table fields.
Hope this helps.
I can't find any info about this in the documentation, so I will ask here. How does breeze handle database column defaults? I have required columns in my database, but there are also default static values supplied for these in the database column definitions. Normally, I can insert null into these columns, and the new records will get the default. However, breeze doesn't seem to be aware of database column defaults, and the entities that have null in these columns fail validation on saving.
Thanks,
Mathias
Try editing the edmx xml by adding StoreGeneratedPattern = "Computed" attribute to the column with default value in the DB.
Edit:
Actually, before doing editing the xml, try setting the StoreGeneratedPattern property to Computed in the model editor itself.
Update:
This was fixed in Breeze 1.4.6 ( or later), available now.
Original Post:
There is currently in a bug in Breeze that should be fixed in the next release, out in about week. When this fix gets in then breeze will honor any defaultValues it finds in the EntityFramework data model.
One problem though is while it is easy to get 'defaultValues' into a Model First Entity Framework model via the properties editor, it's actually difficult to get it into a Code First EF model, unless you use fluent configuration. Unfortunately, EF ignores the [DefaultValue] attribute when constructing Code First model metadata.
One workaround that you can use now is to poke the 'defaultValue' directly onto any dataProperty. Something like:
var customerType = myEntityManager.metadataStore.getEntityType("Customer");
var fooProperty = customerType.getProperty("foo");
fooProperty.defaultValue = 123;
I'm using an MVC webform to insert a record into a database with several subrecords. In my code-behind I'm first creating a new main record using dataRepository.Add(xx). Now I need to add 5 subrecords that need the ID of the newly created record. How can I retrieve that?
Assuming xx is your model, and its primary key is Id you can get the Id of your inserted record like this:
// at this point xx.Id == null
db.XX.AddObject(xx);
db.SaveChanges();
// now: xx.Id > 0
int id = xx.Id;
If you are using an ORM such as Entity Framework you should be able to create the record and the associated records, link them by adding the associated records into a collection on the main object or setting them somehow and then call the save method on the context. This will do all the linking with ids etc. for you.
How are you doing data access?
You should probably submit all 5 records plus the main one all the way down to your datalayer, performing any validation on the way in your business layer. Then, depending on the implementation of your DL, save the main record, returning the ID, set the parent ID on the subrecords and save them. Do it all within a single transaction and you should be ok.
Please give more info on your data access layer.
If using MS SQL Server, you would use the Scope_Identity() within your stored procedure to get the last identity value inserted into an identity column. See this MSDN article
If using NHibernate you add them within the same session and NHibernate takes care of generating the SQL responsible for inserting the records with the correct Ids.
I have a Client entity and PostCode entity in Linq to SQL model. The Clients table in database contains client_postcode column which is a FK column to postalcode column in PostCode table, which is a varchar column primary key for PostCode table.
When updating Client, in my code I do this
// postcode
updating.PostCode = (from p in ctx.PostCodes
where p.postalcode.Equals(client.PostCode.postalcode)
select p).First();
where client object is provided from ASP.NET MVC View form. This code seems to set the PostCode related entity fine. But when calling SubmitChanges() I receive the following exception:
Value of member 'postalcode' of an object of type 'PostCode' changed. A member defining the identity of the object cannot be changed. Consider adding a new object with new identity and deleting the existing one instead.
So I am currently unable to change the related entity. How is that done in Linq to Sql?
UPDATE:
After further review and troubleshooting I found out that the problem is in ASP.NET MVC UpdateModel() call. If I call UpdateModel() to update the existing entity with the edited data, something is wrong with the FK assignement for PostCode. If I don't call UpdateModel and do it by hand, it works.
Any ideas what goes wrong in UpdateModel() that it can't set the relationship to foreign key entities correctly?
I am updating this question and starting a bounty. The question is simplified. How to successfully use L2S and UpdateModel() to work when updating items (with related entities as FK) in ASP.NET MVC Edit views?
It seems to me that you are receiving PostCode.postalcode in the http post request.
Based on how model binding works, the UpdateModel call updates .PostCode.postalcode of the model you are passing to it.
Use this overload to include or exclude specific properties.
Wouldn't updating.client_postcode = client.client_postcode; accomplish what you want?
Client.PostCode should be looked up on seek based on client_postocde.
You can not do what you are trying, you cannot change the Postcode like that.
James' idea is in the right direction.
Updatemodel() takes the matching values from the Formcollection
How do these values come in the Formcollection? What are their keys?
basically there are 2 ways in editing an object.
option 1:
all the value names you want to update have corresponding keys in the Formcollection, which leaves you just to call UpdateModel() of the original object. do SubmitChanges()
option 2:
Get the original object, change it's values manually (because the keys dont correspond) and do SubmitChanges()
you are tying to change a link, you cant do that. you can only edit the updating.client_postcode which in this case is a string?
Can you please copy the whole action here? So I can write some code for you without gambling.