Entity Framework will not SaveChanges for new two-tier entity

Question

I am building an ASP.NET MVC site using the ADO.NET Entity Framework. I have an entity model that includes these entities associated with foreign keys:

Report (ID, Date, Title, Report_Type_ID, etc.)

• SubReport (ID, ReportText, etc.) is a one-to-one relationship with Report.
  • ReportSource (ID, Name, Description) - one-to-many relationship with Sub_Report.
    • ReportSourceType (ID, name, description) - one-to-many relationship with ReportSource.
    • Contact (identifier, name, address, etc.) is a one-to-one relationship with Report_Source.

For each type of SubReport, there is a Create.aspx page. The post post method returns a new Sub_Report object.

Before that, in my post method, I followed this process:

• Set the properties for the new report object from the page fields.
• Set the entity properties specific to SubReport from the page fields.
• Define the report of the SubReport object to the new Report object created in 1.
• Given the identifier provided by the page, find the ReportSource and set the ReportSource object of the Sub_Report object for the found object.
• SaveChanges.

This workflow went well just a couple of weeks. Then last week something changed and it no longer works. Now, instead of the save operation, I get this exception:

UpdateException: "Entities in 'DIR2_5Entities.ReportSourceSet' 
participate in the 'FK_ReportSources_ReportSourceTypes' relationship. 
0 related 'ReportSourceTypes' were found. 1 'Report_Source_Types' is expected."

:

• SubReport ReportSource , .
• Report_Source ReportSourceType.

SQL Profiler SQL . - , ?

: SubReport . Report , , . SubReports - , . SubReport , , SubReport .

Answer 1

, 1 - 1 . reportourceset , reportorttype , . , .

Answer 2

, , , 3 , . , - , - .

:

• SaveChanges() . . , , , . Report_Source_Type.
• , , , . , , , .

context.GetObjectByKey, , context.Attach, .

Answer 3

, , FK, PK.

PK .

Answer 4

, ReportSource NoTracking EntityState == 'Detached'. , , .

Answer 5

- , " " "". .

Answer 6

, , .

:

Pet pet = new Pet();
context.Pets.Add(pet);
// forgot this: petOwner.Pets.Add(pet);