Reattaching an object graph to an EntityContext: "cannot track multiple objects with the same key"
- by dkr88
Can EF really be this bad? Maybe...
Let's say I have a fully loaded, disconnected object graph that looks like this:
myReport =
{Report}
{ReportEdit {User: "JohnDoe"}}
{ReportEdit {User: "JohnDoe"}}
Basically a report with 2 edits that were done by the same user.
And then I do this:
EntityContext.Attach(myReport);
InvalidOperationException: An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key.
Why? Because the EF is trying to attach the {User: "JohnDoe"} entity TWICE.
This will work:
myReport =
{Report}
{ReportEdit {User: "JohnDoe"}}
EntityContext.Attach(myReport);
No problems here because the {User: "JohnDoe"} entity only appears in the object graph once.
What's more, since you can't control how the EF attaches an entity, there is no way to stop it from attaching the entire object graph. So really if you want to reattach a complex entity that contains more than one reference to the same entity... well, good luck.
At least that's how it looks to me. Any comments?
UPDATE: Added sample code:
// Load the report
Report theReport;
using (var context1 = new TestEntities())
{
context1.Reports.MergeOption = MergeOption.NoTracking;
theReport = (from r in context1.Reports.Include("ReportEdits.User")
where r.Id == reportId
select r).First();
}
// theReport looks like this:
// {Report[Id=1]}
// {ReportEdit[Id=1] {User[Id=1,Name="John Doe"]}
// {ReportEdit[Id=2] {User[Id=1,Name="John Doe"]}
// Try to re-attach the report object graph
using (var context2 = new TestEntities())
{
context2.Attach(theReport); // InvalidOperationException
}
