I have a registration form that allows a school to register. In addition to the obvious login and general details the school can pick from a list of facilities and accreditations that they have.
My data is displayed lovely and binded correctly.
Problem Entering the data into the linker tables does not work it throws an error in both the different ways that I have tried:
Method1:
MembershipUser membershipUser = null;
if (schoolRegisterModel != null)
{
if (null != DB)
{
school SchoolUser = new school();
SchoolUser.username = schoolRegisterModel.UserName;
SchoolUser.email = schoolRegisterModel.Email;
string sPassowrdSalt = Security.Instance().CreateSalt();
SchoolUser.password = Security.Instance().CreatePasswordHash(schoolRegisterModel.Password, sPassowrdSalt);
SchoolUser.password_salt = sPassowrdSalt;
..More data etc..
foreach (var item in schoolRegisterModel.Facilities)
{
if (item.#checked)
{
school_facility sf = new school_facility();
sf.facility_id = item.facility_id;
SchoolUser.school_facility.Add(sf);
}
}
foreach (var item in schoolRegisterModel.Accreditations)
{
if (item.#checked)
{
school_accreditation sa = new school_accreditation();
sa.accreditation_id = item.accreditation_id;
SchoolUser.school_accreditation.Add(sa);
}
}
DB.schools.Add(SchoolUser);
DB.SaveChanges();
Error: {"The INSERT statement conflicted with the FOREIGN KEY constraint \"FK_school_facility_facility\". The conflict occurred in database \"MYDB\", table \"dbo.facility\", column 'facility_id'.\r\nThe statement has been terminated."}
Also - Do I need to manually retrieve the soon to be school ID that will be generated based on this insert. This method avoids entering data directly into the linker tables using only the primary table (school).
Method2:
Same code again apart from trying to update the primary tables (school) accreditation and facilities collection directly, I manually update the linker tables seperately using the latest primary key generated by the previous query, code for this is as follows:
MembershipUser membershipUser = null;
if (schoolRegisterModel != null)
{
if (null != DB)
{
school SchoolUser = new school();
SchoolUser.username = schoolRegisterModel.UserName;
SchoolUser.email = schoolRegisterModel.Email;
string sPassowrdSalt = Security.Instance().CreateSalt();
SchoolUser.password = Security.Instance().CreatePasswordHash(schoolRegisterModel.Password, sPassowrdSalt);
SchoolUser.password_salt = sPassowrdSalt;
..More data etc..
// Linker data for facilities and accreditations.
// Facilities
foreach (var item in schoolRegisterModel.Facilities)
{
if (item.#checked)
{
school_facility sf = new school_facility();
sf.facility_id = item.facility_id;
sf.school_id = SchoolUser.school_id;
DB.school_facility.Add(sf);
}
}
// Accreditations
foreach (var item in schoolRegisterModel.Accreditations)
{
if (item.#checked)
{
school_accreditation sa = new school_accreditation();
sa.accreditation_id = item.accreditation_id;
sa.school_id = SchoolUser.school_id;
DB.school_accreditation.Add(sa);
}
}
m_DB.SaveChanges();
Error: {"The INSERT statement conflicted with the FOREIGN KEY constraint \"FK_school_facility_facility\". The conflict occurred in database \"MYDB\", table \"dbo.facility\", column 'facility_id'.\r\nThe statement has been terminated."}
If you guys have any idea where I am going wrong then please do let me know. There seem to be examples of updating linker table date (which I will need at some point anyway) but can't find an example of my problem...
Thanks in advance.
Looks like I have found the answer:
MVC: The INSERT statement conflicted with the FOREIGN KEY constraint
My data being pulled through was basically not containing the correct foreign key value (0 - which didn't exist) and quite rightly my DB was throwing the error. Sorry for wasting time to whoever read and thanks for your time. I hope this can help somebody else.
Joe
Related
I have a flatfile from a different database. I import it and map it to my application's entities. Because the flatfile does not contain ids I cannot be sure the entries I handle are not duplicates of what has already been added to my database earlier or to my context at this moment.
The error message I get is:
The instance of entity type 'Car' cannot be tracked because another
instance with the same key value for {'Make', 'Model'} is already
being tracked. When attaching existing entities, ensure that only one
entity instance with a given key value is attached. Consider using
'DbContextOptionsBuilder.EnableSensitiveDataLogging' to see the
conflicting key values.
An example:
Data rows from flatfile
Volvo V70 Steve
Volvo V70 John
Having mapped these rows and trying to put them in db
foreach(var row in flatFileRows){
Car existingCar = null;
if(dbContext.Cars.Any(c => c.Make == row.Make && c.Model == row.Model)){
existingCar = dbContext.Cars
.SingleOrDefault(c => c.Make == row.Make && c.Model == row.Model);
}
//I also do the same for existingDriver
var car = existingCar != null
? existingCar
: new Car()
{
Make = row.Make,
Model = row.Model,
Drivers = new List<Driver>();
};
var driver = new Driver()
{
CarId = existingCar != null ? exsitingCar.Id : 0,
Name = row.Name
};
car.Drivers.Add(driver);
dbContext.Cars.Update(car); //Second time we hit this the error is thrown
}
dbContext.SaveChanges();
Make and Model are set to keys in the schema because I don't want duplicate entries of the car models.
The above example is simplified.
What I want is to check if I already put a car in the db with these attributes and then build according to my schema from that entity. I don't care to track any entries, disconnected or otherwise, because I just need to populate the database.
I need to add a record to a database using the Entity Framework. Since I'm brand new to using this syntax I am not sure how to properly write the code (Below is my best guess).
First, the agent must have their info inserted into the Agent table. This table produces a self-incrementing primary key known as a SymNumber. I then need to take that SymNumber and use it as a primary key for an insert into the AgentIdentification table.
I have run this code a couple of times, and I do not come up with an error, however since I am using a unit test to test the code I cannot tell for sure if the agent is being added properly. Secondly, I know for a fact that I am not correctly grabbing the SymNumber as generated by the Agent table after the first insert. The SymNumber is an int value in the Linq code set to 0, and this does not change during the AgentIdentification insert.
Any help would be greatly appreciated!
AgentResourcesEntities _db = new AgentResourcesEntities();
try
{
Agent agent = new Agent();
agent.EntityType = "P";
agent.FirstName = agentNewTraining.FirstName;
agent.LastName = agentNewTraining.LastName;
agent.LastChangeOperator = agentNewTraining.Requestor;
agent.LastChangeDate = DateTime.Now;
if (!String.IsNullOrEmpty(agentNewTraining.NameSuffix)) agent.NameSuffix = agentNewTraining.NameSuffix;
_db.Agent.AddObject(agent);
AgentIdentification agentIdentification = new AgentIdentification();
agentIdentification.SymNumber = agent.SymNumber;
agentIdentification.ReferenceType = "S";
agentIdentification.DummyReference = 0;
agentIdentification.LastChangeOperator = agentNewTraining.Requestor;
agentIdentification.LastChangeDate = DateTime.Now;
_db.AgentIdentification.AddObject(agentIdentification);
return true;
}
catch (Exception)
{
return false;
}
First you need to call
_db.SaveChanges();
to get your changed persisted.
But if you want also synchronize (get the new generated value) your agent.SymNumber you will need to call SaveChanges() right after adding it to context.
So the code will be like:
/// ...... ////
_db.Agent.AddObject(agent);
_db.SaveChanges();
AgentIdentification agentIdentification = new AgentIdentification();
agentIdentification.SymNumber = agent.SymNumber; // sym number is now synchronized from DB
///...../////
_db.AgentIdentification.AddObject(agentIdentification);
_db.SaveChanges();
But if SymNumber is foreign key so the AgentIdentification has could have reference to some Agent instance, you can just tie those instances with that reference and would not need to call that additional SaveChanges() in the middle.
Call _db.SaveChanges() after inserting.
I have a table named countries and i define the country_name field to be unique by creating a “Index/Key” of type “Unique Key” on sql servwer 2008 r2.
But currently if the user insert a country_name value that already exists on my asp.net mvc3 application, then an exception of type “System.Data.Entity.Infrastructure.DbUpdateException” will be raised , which is very general.
So is there a way to define a specific exception in case the unique constraint has been violated ??? rather than just raising the general “System.Data.Entity.Infrastructure.DbUpdateException” exception?
BR
Most likely, thought I can't test it at the moment, the inner exception of DbUpdateException is probably an exception about a duplicate or foreign key constraint. More importantly, you have an opportunity to not throw any exceptions by checking to see if a country already exists. Two ways I can think of are to; check and see if the country already exists by doing a simple select, and if it doesn't, doing an insert/add or write a stored procedure that and do a select/insert or merge and return any value(s) you want back.
Update
(this is example code to demonstrate the logic flow of events and not good programming practice, specially by catching all excepts)
Exception Logic
public AddCountry(string countryTitle)
{
using (var db = new DbContext(_connectionString)
{
try
{
// Linq to (SQL/EF)-ish code
Country country = new Country();
country.ID = Guid.NewGuid();
country.Title = countryTitle;
db.Countrys.Add(country);
db.SubmitChanges(); // <--- at this point a country could already exist
}
catch (DbUpdateException ex)
{
// <--- at this point a country could be delete by another user
throw Exception("Country with that name already exists");
}
}
}
Non-Exception Logic
public AddCountry(string countryTitle)
{
using (var db = new DbContext(_connectionString)
{
using (TransactionScope transaction = new TransactionScope())
{
try
{
Country country = db.Countries
.FirstOrDefault(x => x.Title = countryTitle);
if (country == null)
{
country = new Country();
country.ID = Guid.NewGuid();
country.Title = countryTitle;
db.Countrys.Add(country);
db.SubmitChanges(); // <--- at this point a country
// shouldn't exist due to the transaction
// although someone with more expertise
// on transactions with entity framework
// would show how to use transactions properly
}
}
catch (<someTimeOfTransactionException> ex)
{
// <--- at this point a country with the same name
// should not exist due to the transaction
// this should really only be a deadlock exception
// or an exception outside the scope of the question
// (like connection to sql lost, etc)
throw Exception("Deadlock exception, cannot create country.");
}
}
}
}
Most likely the TransactionScope(Transaction transactionToUse) Constructor would be needed and configured properly. Probably with an Transactions.IsolationLevel set to Serializable
I would also recommend reading Entity Framework transaction.
I have code that generates records based on my DataGridView. These records are temporary because some of them already exist in the database.
Crop_Variety v = new Crop_Variety();
v.Type_ID = currentCropType.Type_ID;
v.Variety_ID = r.Cells[0].Value.ToString();
v.Description = r.Cells[1].Value.ToString();
v.Crop = currentCrop;
v.Crop_ID = currentCrop.Crop_ID;
Unfortunately in this little bit of code, because I say that v.Crop = currentCrop,
now currentCrop.Crop_Varieties includes this temporary record. And when I go to insert the records of this grid that are new, they have a reference to the same Crop record, and therefore these temporary records that do already exist in the database show up twice causing duplicate key errors when I submit.
I have a whole system for detecting what records need to be added and what need to be deleted based on what the user has done, but its getting gummed up by this relentless tracking of references.
Is there a way I can stop Linq-To-Sql from automatically adding these temporary records to its table collections?
I would suggest revisiting the code that populates DataGridView (grid) with records.
And then revisit the code that operates on items from a GridView, keeping in mind that you can grab bound item from a grid row using the following code:
public object GridSelectedItem
{
get
{
try
{
if (_grid == null || _grid.SelectedCells.Count < 1) return null;
DataGridViewCell cell = _grid.SelectedCells[0];
DataGridViewRow row = _grid.Rows[cell.RowIndex];
if (row.DataBoundItem == null) return null;
return row.DataBoundItem;
}
catch { }
return null;
}
}
It is also hard to understand the nature of Crop_Variety code that you have posted. As the Crop_Variety seems to be a subclass of Crop. This leads to problems when the Crop is not yet bound to database and potentially lead to problems when you're adding Crop_Variety to the context.
For this type of Form application I normally have List _dataList inside form class, then the main grid is bound to that list, through ObjectBindingList or another way. That way _dataList holds all data that needs to be persisted when needed (user clicked save).
When you assign an entity object reference you are creating a link between the two objects. Here you are doing that:
v.Crop = currentCrop;
There is only one way to avoid this: Modify the generated code or generate/write your own. I would never do this.
I think you will be better off by writing a custom DTO class instead of reusing the generated entities. I have done both approaches and I like the latter one far better.
Edit: Here is some sample generated code:
[global::System.Data.Linq.Mapping.AssociationAttribute(Name="RssFeed_RssFeedItem", Storage="_RssFeed", ThisKey="RssFeedID", OtherKey="ID", IsForeignKey=true, DeleteOnNull=true, DeleteRule="CASCADE")]
public RssFeed RssFeed
{
get
{
return this._RssFeed.Entity;
}
set
{
RssFeed previousValue = this._RssFeed.Entity;
if (((previousValue != value)
|| (this._RssFeed.HasLoadedOrAssignedValue == false)))
{
this.SendPropertyChanging();
if ((previousValue != null))
{
this._RssFeed.Entity = null;
previousValue.RssFeedItems.Remove(this);
}
this._RssFeed.Entity = value;
if ((value != null))
{
value.RssFeedItems.Add(this);
this._RssFeedID = value.ID;
}
else
{
this._RssFeedID = default(int);
}
this.SendPropertyChanged("RssFeed");
}
}
}
As you can see the generated code is establishing the link by saying "value.RssFeedItems.Add(this);".
In case you have many entities for wich you would need many DTOs you could code-generate the DTO classes by using reflection.
After going through Entity Framework I have a couple of questions on implementing auditing in Entity Framework.
I want to store each column values that is created or updated to a different audit table.
Right now I am calling SaveChanges(false) to save the records in the DB(still the changes in context is not reset). Then get the added | modified records and loop through the GetObjectStateEntries. But don't know how to get the values of the columns where their values are filled by stored proc. ie, createdate, modifieddate etc.
Below is the sample code I am working on it.
// Get the changed entires( ie, records)
IEnumerable<ObjectStateEntry> changes = context.ObjectStateManager.GetObjectStateEntries(EntityState.Modified);
// Iterate each ObjectStateEntry( for each record in the update/modified collection)
foreach (ObjectStateEntry entry in changes)
{
// Iterate the columns in each record and get thier old and new value respectively
foreach (var columnName in entry.GetModifiedProperties())
{
string oldValue = entry.OriginalValues[columnName].ToString();
string newValue = entry.CurrentValues[columnName].ToString();
// Do Some Auditing by sending entityname, columnname, oldvalue, newvalue
}
}
changes = context.ObjectStateManager.GetObjectStateEntries(EntityState.Added);
foreach (ObjectStateEntry entry in changes)
{
if (entry.IsRelationship) continue;
var columnNames = (from p in entry.EntitySet.ElementType.Members
select p.Name).ToList();
foreach (var columnName in columnNames)
{
string newValue = entry.CurrentValues[columnName].ToString();
// Do Some Auditing by sending entityname, columnname, value
}
}
Here you have two basic options:
Do it at the database level
Do it in the c# code
Doing it at the data base level, means using triggers. In that case there is no difference if you are using enterprise library or another data access technology.
To do it in the C# code you would add a log table to your datamodel, and write the changes to the log table. When you do a save changes both the changes to the data and the information which you wrote to the log table would be saved.
Are you inserting the new record using a stored proc? If not (i.e. you are newing up an object, setting values, inserting on submit and then saving changes the new object id will be automatically loaded into the id property of the object you created. If you are using a stored proc to do the insert then you need to return the ##IDENTITY from the proc as a return value.
EX:
StoreDateContext db = new StoreDataContext(connString);
Product p = new Product();
p.Name = "Hello Kitty Back Scratcher";
p.CategoryId = 5;
db.Products.Add(p);
try
{
db.SaveChanges();
//p.Id is now set
return p.Id;
}
finally
{
db.Dispose;
}