使用EF 6中的导航属性删除

Question

I am using EF 6 database modal in my application. I have a table TBL_USER which has 1:N relationship in some other table. One of them is TBL_USER_CASE where primary key of TBL_USER act as foreign key in TBL_USER_CASE .

Now i am deleting some user from TBL_USER . Before that i need to delete corresponding entries in TBL_USER_CASE . I am using following code for that

 private long DeleteUser(long UserID)
    {
        using(VerbaTrackEntities dataContext = new VerbaTrackEntities())
        {
            TBL_USER user = dataContext.TBL_USER.Where(x => x.LNG_USER_ID == UserID).SingleOrDefault();
            if(user != null)
            {
                foreach (var cases in user.TBL_USER_CASE.ToList())
                {
                    user.TBL_USER_CASE.Remove(cases);                          
                }
            }
            dataContext.SaveChanges();
        }
        return 0;
    }

Here im getting exception

Additional information: 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

How can i do this operation correctly ??

Answer 1

Ok, if your goal is to delete the user, you can let the framework handle the child-relations. You can try this:

private long DeleteUser(long UserID)
{
    using(VerbaTrackEntities dataContext = new VerbaTrackEntities())
    {
        TBL_USER user = dataContext.TBL_USER.
                                 SingleOrDefault(x => x.LNG_USER_ID == UserID);
        if(user != null)
        {       
            dataContext.TBL_USER.Remove(user); 
            dataContext.SaveChanges();
        }
    }
    return 0;
}

Update: can you try this one:

private long DeleteUser(long UserID)
{
    using(VerbaTrackEntities dataContext = new VerbaTrackEntities())
    {
        TBL_USER user = dataContext.TBL_USER
                             .SingleOrDefault(x => x.LNG_USER_ID == UserID);
        if(user != null)
        {
            foreach (var cases in user.TBL_USER_CASE.ToList())
            {
                //little modification is here
                dataContext.TBL_USER_CASE.Remove(cases);                          
            }
        }
        dataContext.SaveChanges();
    }
    return 0;
}

Answer 2

I managed to do so himself by reading through the net. I have done this by

 System.Data.Entity.Core.Objects.ObjectContext oc = ((System.Data.Entity.Infrastructure.IObjectContextAdapter)dataContext).ObjectContext;
 foreach(var Cases in user.TBL_USER_CASE.ToList())
    {                        
       oc.DeleteObject(Cases);                       
    }                    
    oc.SaveChanges();
    dataContext.TBL_USER.Remove(user);