Question

Lets assume the following code handling the SaveChanges event of a DataContext

void Context_SavingChanges(object sender, EventArgs e)
    {

        IEnumerable<ObjectStateEntry> objectStateEntries =
            from ose in this.ObjectStateManager.GetObjectStateEntries(EntityState.Added | EntityState.Modified | EntityState.Deleted)
            where ose.Entity != null
            select ose;

        foreach (ObjectStateEntry entry in objectStateEntries)
        {
            foreach (var field in entry.CurrentValues.DataRecordInfo.FieldMetadata)
            {
                var guid = Guid.NewGuid();
                AuditEntry audit = AuditEntry.CreateAuditEntry(
                    id: guid,
                    entitySet: entry.EntitySet.Name,
                    typeName: entry.Entity.GetType().Name,
                    entityId: (entry.CurrentValues["Id"] as string) ?? ((entry.State == EntityState.Added) ? "New" : null),
                    oldValue: (entry.State != EntityState.Added) ? entry.OriginalValues[field.FieldType.Name].ToString() : "New",
                    newValue: (entry.State != EntityState.Deleted) ? entry.CurrentValues[field.FieldType.Name].ToString() : "Deleted",
                    modifier: Environment.UserDomainName + "\\" + Environment.UserName,
                    dbAction: Enum.GetName(typeof(EntityState), entry.State),
                    field: field.FieldType.Name,
                    dateStamp: DateTime.Now
                );


                this.AuditEntries.AddObject(audit);
            }
        }
    }

When I create a new Entity and attempt to save it’s changes I get this error:

Cannot insert the value NULL into column ‘Id’, table ‘TimeEF.dbo.AuditEntries’; column does not allow nulls. INSERT fails.
The statement has been terminated.

When as you can see I have set the Id, any ideas? Bug?

Answer 1

Have you examined the id column of your object in the EDMX file? If its StoreGeneratedPattern attribute is marked as “computed” or “identity”, then EF will not carry the C# value over to its SQL statement. Set the StoreGeneratedPattern attribute to “None” and the SQL that Entity Framework writes will contain your C#-created value for id.

<EntityType Name="AuditEntry">
    //...
    <Property Name="id" Type="int" Nullable="false" StoreGeneratedPattern="None" />
    //...
</EntityType>

For more information, see http://msdn.microsoft.com/en-us/library/dd296755(v=vs.90).aspx.