I am using the ADO entity framework for the first time and am not sure of the best way of inserting db recored that contain foreign keys.
this is the code that i am using, I would appreciate any comments and suggestion on this.
using (KnowledgeShareEntities entities = new KnowledgeShareEntities())
{
Questions question = new Questions();
question.que_title = questionTitle;
question.que_question_text = questionText;
question.que_number_of_views = 0;
question.que_is_anonymous = isAnonymous;
question.que_last_activity_datetime = DateTime.Now;
question.que_timestamp = DateTime.Now;
question.CategoriesReference.Value = Categories.CreateCategories(categoryId);
question.UsersReference.Value = Users.CreateUsers(userId);
entities.AddToQuestions(question);
entities.SaveChanges();
return question.que_id;
}
You should use something like
question.UsersReference.EntityKey = new EntityKey("MyEntities.Users",
"ID", userId);
You don't have to have User object to set up foreign key, just use ID.
Related
I want to log new and modified records. This code works just fine for Modified Records.
But with Added records, there is an issue. Since it is new to the Database, there is not yet a primary key for it. So there is no way to log which record was added.
However, if I try to log the records after the save, the EntityState is no longer Added. So I don't know what was added.
The only solution I have been able to come up with is to save a list of the new records, and then after the save, then Log the changes. But that seems like a workaround.
Is there some way to resolve this?
private List<Event> LogChanges(EntityEntry entityEntry, Enums.TableNames tableName)
{
List<Event> result = new List<Event>();
var databaseValues = entityEntry.GetDatabaseValues();
foreach (var property in entityEntry.CurrentValues.Properties.Where(a=> a.Name !="TenantId"))
{
string original = databaseValues[property]?.ToString();
string current = entityEntry.CurrentValues[property]?.ToString();
if(!object.Equals(original,current))
{
result.Add(
new Event()
{
AppUserId = this._appUserProvider.CurrentAppUserId,
EventDate = DateTimeOffset.UtcNow,
EventTypeId = (int)Enums.EventTypes.Modified,
TenantId = databaseValues.GetValue<int>("TenantId"),
RecordId = databaseValues.GetValue<int>("Id"),
ColumnName = property.Name,
OriginalValue = original,
NewValue = current,
TableId = (int)tableName
});
}
}
return result;
}
This library adds triggers to EntityFrameworkCore. Using the Triggers it provides is a much cleaner way to accomplish the above.
I have an object with several really large string properties. In addition, it has a simple timestamp property.
What I trying to achieve is to update only timestamp property without getting the whole huge object to the server.
Eventually, I would like to use EF and to do in the most performant way something equivalent to this:
update [...]
set [...] = [...]
where [...]
Using the following, you can update a single column:
var yourEntity = new YourEntity() { Id = id, DateProp = dateTime };
using (var db = new MyEfContextName())
{
db.YourEntities.Attach(yourEntity);
db.Entry(yourEntity).Property(x => x.DateProp).IsModified = true;
db.SaveChanges();
}
OK, I managed to handle this. The solution is the same as proposed by Seany84, with the only addition of disabling validation, in order to overcome issue with required fields. Basically, I had to add the following line just before 'SaveChanges():
db.Configuration.ValidateOnSaveEnabled = false;
So, the complete solution is:
var yourEntity = new YourEntity() { Id = id, DateProp = dateTime };
using (var db = new MyEfContextName())
{
db.YourEntities.Attach(yourEntity);
db.Entry(yourEntity).Property(x => x.DateProp).IsModified = true;
db.Configuration.ValidateOnSaveEnabled = false;
db.SaveChanges();
}
I've been using JPA to insert entities into a database but I've run up against a problem where I need to do an insert and get the primary key of the record last inserted.
Using PostgreSQL I would use an INSERT RETURNING statement which would return the record id, but with an entity manager doing all this, the only way I know is to use SELECT CURRVAL.
So the problem becomes, I have several data sources sending data into a message driven bean (usually 10-100 messages at once from each source) via OpenMQ and inside this MDB I persists this to PostgreSQL via the entity manager. It's at this point I think there will be a "race condition like" effect of having so many inserts that I won't necessarily get the last record id using SELECT CURRVAL.
My MDB persists 3 entity beans via an entity manager like below.
Any help on how to better do this much appreciated.
public void onMessage(Message msg) {
Integer agPK = 0;
Integer scanPK = 0;
Integer lookPK = 0;
Iterator iter = null;
List<Ag> agKeys = null;
List<Scan> scanKeys = null;
try {
iag = (IAgBean) (new InitialContext()).lookup(
"java:comp/env/ejb/AgBean");
TextMessage tmsg = (TextMessage) msg;
// insert this into table only if doesn't exists
Ag ag = new Ag(msg.getStringProperty("name"));
agKeys = (List) (iag.getPKs(ag));
iter = agKeys.iterator();
if (iter.hasNext()) {
agPK = ((Ag) iter.next()).getId();
}
else {
// no PK found so not in dbase, insert new
iag.addAg(ag);
agKeys = (List) (iag.getPKs(ag));
iter = agKeys.iterator();
if (iter.hasNext()) {
agPK = ((Ag) iter.next()).getId();
}
}
// insert this into table always
iscan = (IScanBean) (new InitialContext()).lookup(
"java:comp/env/ejb/ScanBean");
Scan scan = new Scan();
scan.setName(msg.getStringProperty("name"));
scan.setCode(msg.getIntProperty("code"));
iscan.addScan(scan);
scanKeys = (List) iscan.getPKs(scan);
iter = scanKeys.iterator();
if (iter.hasNext()) {
scanPK = ((Scan) iter.next()).getId();
}
// insert into this table the two primary keys above
ilook = (ILookBean) (new InitialContext()).lookup(
"java:comp/env/ejb/LookBean");
Look look = new Look();
if (agPK.intValue() != 0 && scanPK.intValue() != 0) {
look.setAgId(agPK);
look.setScanId(scanPK);
ilook.addLook(look);
}
// ...
The JPA spec requires that after persist, the entity be populated with a valid ID if an ID generation strategy is being used. You don't have to do anything.
currently I'm Inserting like:
MyNamedEntities db = new MyNamedEntities();
MyTableEntity field = new MyTableEntity();
field.Name = "me";
db.MyTableEntity.AddObject(field);
db.SaveChanges()
But now I want to insert child elements and I need that field.Id part
MyOtherTableEntity field = new MyOtherTableEntity();
field.TableId = new MyTableEntity.First(x => x.Id.Equals( ... ));
How can I get the field.Id ?
If your table has defined the Id as an INT IDENTITY column, then you don't really have to do anything at all! :-)
In that case, just insert your entity and after the call to .SaveChanges(), your object should contain the new Id value:
MyTableEntity field = new MyTableEntity();
field.Name = "me";
db.MyTableEntity.AddObject(field);
db.SaveChanges();
int newID = field.Id;
You can also just add them to the parent by the association before or after the save changes
Something like this.
address a = new address();
a.city = "Detroit";
field.address.add(a);
db.SaveChanges();
I am having a real issue with the EF v1. I have quite a big EDMX with maybe 50 entities mapped, but this one entity is causing me grief.
The entity has mappings to other entities which in effect are reference tables, but for some reason it is trying to do an insert and not just update itself.
Here is a fragment of my code:
using (var context = new someEntities()) {
var studentCourseJoin =
context.StudentCourseJoinSet.Where(o => o.Code == scjCode).First();
studentCourseJoin.EntryStatus = new EntryStatus { Code = viewModel.StudentDetails.EntryStatusCode };
studentCourseJoin.ParentalInHigherEducation = new ParentalInHigherEducation { Code = viewModel.StudentDetails.ParentalInHigherEducationCode };
studentCourseJoin.School = new School { Code = viewModel.StudentDetails.SchoolCode };
studentCourseJoin.Institution = new Institution { Code = viewModel.StudentDetails.InstitutionCode };
studentCourseJoin.LastSchoolEndYear = viewModel.StudentDetails.LastSchoolEndYear;
studentCourseJoin.LastInstitutionEndYear = viewModel.StudentDetails.LastInstitutionEndYear;
// Blows up here trying to do an insert on the studentCourseJoin.Institution.
// But if I removed this one, then it will blow up on another one.
context.SaveChanges(true);
}
If anyone has ANY ideas please, they would help a lot.
Try adding those lines before calling SaveChanges:
ObjectStateEntry entry = context.ObjectStateManager.GetObjectStateEntry(studentCourseJoin);
entry.ChangeState(EntityState.Modified);
Update:
Try this for Institution instead:
studentCourseJoin.Institution = context.Institutions.FirstOrDefault(i => i.Code == viewModel.StudentDetails.InstitutionCode);