c# - 删除实体时出现错误 : The relationship could not be changed because one or more of the foreign-key properties is non-nullable

Question

我的模型如图所示。

代码:

            App MyApp = (App)Application.Current;

            WFE = new WorkflowMenuEntities();
            WFE.Database.Connection.ConnectionString = MyApp.WorkflowMenuEntityConnectionString;


            string Input = Microsoft.VisualBasic.Interaction.InputBox("Deleting this Business Area will delete ALL processes associated with it.  If you are sure you wish to continue please type in delete and press ok.", "Confirm Deletion");

            if (Input == "delete")
            {
                int BusinessID = ((BusinessArea)ComboboxBusinessArea.SelectedItem).ID;

                BusinessArea myBusinessArea = WFE.BusinessAreas.Where(BA => BA.ID == BusinessID).FirstOrDefault();

                foreach (var myProcesses in myBusinessArea.Processes.ToList())
                {

                    foreach (var myWorkerProcess in myProcesses.WorkerProcesses.ToList())
                    {

                        myProcesses.WorkerProcesses.Remove(myWorkerProcess);


                    }

                    myBusinessArea.Processes.Remove(myProcesses);

                }

                foreach (var myADGroup in myBusinessArea.ADGroups.ToList())
                {
                    myBusinessArea.ADGroups.Remove(myADGroup);
                }



                WFE.BusinessAreas.Remove(myBusinessArea);
                WFE.SaveChanges();

                BuildBusinessAreaList();


            }

每当我运行此代码时，它都会在 WFE.SaveChanges 行出现以下错误。

System.InvalidOperationException: 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. at System.Data.Objects.ObjectContext.SaveChanges(SaveOptions options)
at System.Data.Entity.Internal.InternalContext.SaveChanges() at System.Data.Entity.Internal.LazyInternalContext.SaveChanges() at System.Data.Entity.DbContext.SaveChanges() at ManageBusinessAreas.MainWindow.ButtonDeleteBusinessArea_Click(Object sender, RoutedEventArgs e) in c:\TFS_Source\SharedApps\AdminProcesses\ManageBusinessAreas\ManageBusinessAreas\ManageBusinessAreas\MainWindow.xaml.cs:line 249

我查看了其他帖子，不幸的是，这些修复要么不适用于我，要么不起作用。任何帮助将不胜感激。

Answer 1

发现问题。我不需要从 myBusinessAreas 的流程导航中删除 myProcess，而是需要将其从上下文的流程实体中删除。