在实体框架中创建新实体时违反唯一约束

Question

I have, errr had a working wpf application that manipulates database info (using Entity Framework, database first).

The structure of the data is 4 tables of finance info (all 1:1 mapped to the main table of the 5), with a couple of lookup tables with foreign key refs in the main table.

I added a table (another 1:1 mapping to the main table) in SqlServer and then ran the 'Update Model from Database...' wizard to add the new table to the model. Everything looks alright in the .edmx file, including the '0..1' relationship link.

However, when I try to save, I am receiving a 'Violation of Unique Constraint' error.

My creation code:

private void AddNewStatementsQuery(LGFinanceEntities lGFinanceEntities)
{
  StatementsMain newStatement = StatementsMain.CreateStatementsMain(9999, this.LocalGovt.StakeholderID, 161, this.Year.FinancialYearID);
  StatementsIncome newInc = StatementsIncome.CreateStatementsIncome(newStatement.StatementsMainID);
  StatementsNote newNote = StatementsNote.CreateStatementsNote(newStatement.StatementsMainID);
  StatementsRSSFinPos newRSSFinPos = StatementsRSSFinPos.CreateStatementsRSSFinPos(newStatement.StatementsMainID);
  StatementsSurplusDeficit newSurplusDeficit = StatementsSurplusDeficit.CreateStatementsSurplusDeficit(newStatement.StatementsMainID);
  lGFinanceEntities.StatementsMains.Context.AddObject("StatementsMains", newStatement);
  lGFinanceEntities.StatementsMains.Context.AddObject("StatementsIncomes", newInc);
  lGFinanceEntities.StatementsMains.Context.AddObject("StatementsNotes", newNote);
  lGFinanceEntities.StatementsMains.Context.AddObject("StatementsRSSFinPos", newRSSFinPos);
  lGFinanceEntities.StatementsMains.Context.AddObject("StatementsSurplusDeficit", newSurplusDeficit);
  if (lGFinanceEntities.SaveChanges() != 1)  // this is causing the exception
  {
    MessageBox.Show("Error. New Statements not created", "Database Error");
  }
}

Prior to adding the new table, the above code was working. The only change was the addition of the lines:

StatementsSurplusDeficit newSurplusDeficit = 
    StatementsSurplusDeficit.CreateStatementsSurplusDeficit(newStatement.StatementsMainID);
...
lGFinanceEntities.StatementsMains.Context.AddObject("StatementsSurplusDeficit", 
    newSurplusDeficit);

Interestingly, something is creating a record somewhere, because when I check SqlServer I do have new records for the 5 tables. Also interestingly, each time I try something and run the method, the primary key has been incremented by 2. It looks like the same record is being added twice, but I can't work out how.

Edit: Following a comment suggestion, I changed the 'AddNewStatementsQuery' so lines that looked like:

lGFinanceEntities.StatementsMains.Context.AddObject("StatementsMains", newStatement);

were changed to:

lGFinanceEntities.StatementsMains.AddObject(newStatement);

and then to:

lGFinanceEntities.AddObject("StatementsMains", newStatement);

This did not solve the key violation error.

How do I find out where/how the data is being saved twice (ie, other than lGFinanceEntities.SaveChanges() in the if statement)?

Answer 1

Hmm. Looking at your code, I can see it being simplified down to:

// Create the new objects    
var statement = new StatementsMain()
{
    this.LocalGovt.StakeholderID, 161, this.Year.FinancialYearID
};

var income = new StatementsIncome()
{
    StatementsMain = statement
};

var note = new StatementsNote()
{
    StatementsMain = statement
};

var rss = new StatementsRSSFinPos()
{
    StatementsMain = statement
};

var surplus = new StatementsSurplusDeficit()
{
    StatementsMain = statement
};


// Add the objects into the context 
lGFinancialEntities.AddObject(statement);
lGFinancialEntities.AddObject(income);
lGFinancialEntities.AddObject(note);
lGFinancialEntities.AddObject(rss);
lGFinancialEntities.AddObject(surplus);

// Persist the objects to the data storage
lGFinancialEntities.SaveChanges();

Or, even better:

// Create the main object
var statement = new StatementsMain()
{
    this.LocalGovt.StakeholderID, 161, this.Year.FinancialYearID
};

// Add the objects into the context
lGFinancialEntities.AddObject(statement);
lGFinancialEntities.AddObject(new StatementsIncome() { StatementsMain = statement });
lGFinancialEntities.AddObject(new StatementsNote() { StatementsMain = statement });
lGFinancialEntities.AddObject(new StatementsRSSFinPos() { StatementsMain = statement });
lGFinancialEntities.AddObject(new StatementsSurplusDeficit() { StatementsMain = statement });

// Persist the objects to the data storage
lGFinancialEntities.SaveChanges();

But, this tells me there is a lot about your data schema that's not obvious here. For instance, what does the value 161 reference in the StatementsMain object?

FYI, assigning the primary object to the objects in which it is a foreign-key lets EF do the work of assigning the new ID to the other objects as they are persisted.