EF code first: update entity

Question

I've the following entity:

Partial Public Class Workflow
    Sub New()
        Activities = New List(Of WFActivity)
    End Sub
    <Key()>
    Public Property ID As Long
    Public Property Customer As Customer
    <Required(), MaxLength(100)>
    Public Property Name As String
    Public Property Activities As List(Of WFActivity)
End Class

To add and update an entity I use the following procedure:

Public Sub SaveWorkflow(ByVal WF As Workflow)
    Dim wfa As WFActivity
    Try
        Using ctx = New MyContext

            ctx.Workflow.Add(WF)
            If WF.ID > 0 Then
                ctx.Entry(WF).State = EntityState.Modified
            End If

            For Each wfa In WF.Activities
                If wfa.ID > 0 Then
                    ctx.Entry(wfa).State = EntityState.Modified
                End If
            Next

            If WF.Customer.ID > 0 Then
                ctx.Entry(WF.Customer).State = EntityState.Modified
            End If

            ctx.SaveChanges()
        End Using


    Catch ex As Exception

    End Try
End Function

Inserting a new entity works fine. But using the same WF object for update purpose a second time with this procedure I got the following error:

An error occurred while saving entities that do not expose foreign key properties for their relationships. The EntityEntries property will return null because a single entity cannot be identified as the source of the exception. Handling of exceptions while saving can be made easier by exposing foreign key properties in your entity types. See the InnerException for details.

Where is the bug?

Similar question [here](http://stackoverflow.com/questions/5936880/ef-code-first-4-1-how-to-configure-one-to-many-relationship-with-default). — neizan, Jul 20 '12 at 14:41

score 0 · Answer 1 · answered Nov 13 '12 at 17:07

This happened to me once. I think I solved it just by exposing the keys EF asks for (Exposing the key means the entity holding the reference has also a property that contains the foreign key) e.g:

public class Holder
{
    public Held HeldObject{get;set;}
    public int HeldID //this is the primary key for the entity Held (exact same name)
}

This will create a FK restriction in the DB

EF code first: update entity

1 Answers1