C# EF6 回滚更改，EntityState.Unchanged 错误

Question

// Rollback changes

switch (entry.State)
{
    case EntityState.Added:
        entry.State = EntityState.Detached;
        break;
    case EntityState.Modified:
        entry.CurrentValues.SetValues(entry.OriginalValues);
        entry.State = EntityState.Unchanged;
        break;
    case EntityState.Deleted:
        entry.State = EntityState.Unchanged;
        break;
}

This code is used after EF6 SaveChanges() exception

My scanrio, I insert some values and delete old one then I get an exception. My data should be preserved because of rollback and web site should work normally. But I get this exception in "EntityState.Unchanged" in sector "EntityState.Modified:"

Message=The operation failed: The relationship could not be changed because one or more of the foreign-key properties is non-nullable. When a change is made to a relationship, the related foreign-key property is set to a null value. If the foreign-key does not support null values, a new relationship must be defined, the foreign-key property must be assigned another non-null value, or the unrelated object must be deleted. Source=EntityFramework

Why I can not change DB context back to previous state?

EDIT:

How I delete dependencies?

workReport.sepapayments.Remove(sepaPayment);

workReportAccountSettlement.workreports.Remove(workReport);

Answer 1

the data you are trying to remove have dependent child objects and you have foreign key relation ship setup. therefore you can not delete/add.

Have a look on items you are adding and removing and ensure you have valid entities.

I would split your implementation into two

1st

delete existing items (ensure the dependent child items are removed before you remove parent or use cascade) - if you are using cascade be careful what are you deleting

2nd

add new items once deleting works

Answer 2

Instead of removing the entities from collections

workReport.sepapayments.Remove(sepaPayment);

workReportAccountSettlement.workreports.Remove(workReport);

try to delete them

myDBContext.Entry(sepaPayment).State = System.Data.Entity.EntityState.Deleted;  

myDBContext.Entry(workReport).State = System.Data.Entity.EntityState.Deleted;  

Or you can

myDBContext.ObjectContext.DeleteObject(sepaPayment);

See also this answer . The reason you get this exception is because FK is non-nullable, the UML association between those entites (classes) is a composition, so you need either completely delete the entity or change the FK of the related entity first.