I have the following entites/tables:
Board
: One board can have many pinsPin
: One pin is assigned to one board. This entity is abstract and does have childs with different implementations. All childs belonging to the parent pin entity withInheritanceMapping
and will be saved into the pin table and distinguished by aDiscriminator column
TaskPin
: This is one child implementations of pin. It can have many Tasks.
Task
: One task is assigned to one TaskPin
Here is some code to make my structure more clear:
[Table]
public class Board : ModelBase
{
private int _boardId;
[Column(IsPrimaryKey = true, IsDbGenerated = true, DbType = "INT NOT NULL Identity"
,CanBeNull = false, AutoSync = AutoSync.OnInsert)]
public int BoardId
{
get { return _boardId; }
set { SetProperty(ref _boardId, value); }
}
private EntitySet<Pin> _pins;
[Association(Storage = "_pins", OtherKey = "_boardId"
,ThisKey = "BoardId", DeleteRule = "CASCADE")]
public EntitySet<Pin> Pins
{
get { return _pins; }
set { _pins.Assign(value); }
}
public Board()
{
_pins = new EntitySet<Pin>(new Action<Pin>(this.addPin)
,new Action<Pin>(this.removePin));
}
private void addPin(Pin pin)
{
NotifyPropertyChanging("Pin");
pin.Board = this;
}
private void removePin(Pin pin)
{
NotifyPropertyChanging("Pin");
pin.Board = null;
}
}
[Table]
[InheritanceMapping(Code = PinType.TaskPin, Type = typeof(TaskPin)
,IsDefault = true)]
public abstract class Pin : ModelBase
{
private int _pinId;
[Column(IsPrimaryKey = true, IsDbGenerated = true
,DbType = "INT NOT NULL Identity", AutoSync = AutoSync.OnInsert)]
public int PinId
{
get { return _pinId; }
set { SetProperty(ref _pinId, value); }
}
[Column]
internal int _boardId;
private EntityRef<Board> _board;
[Association(Storage = "_board", ThisKey = "_boardId"
,OtherKey = "BoardId", IsForeignKey = true, DeleteOnNull = true)]
public Board Board
{
get { return _board.Entity; }
set
{
if (SetProperty(ref _board, value) != null)
{
_boardId = value.BoardId;
}
}
}
[Column(IsDiscriminator = true)]
public PinType Type { get; set; }
public Pin()
{
}
}
public class TaskPin : Pin
{
private EntitySet<Task> _tasks;
[Association(Storage = "_tasks", OtherKey = "_pinId"
,ThisKey = "PinId", DeleteRule = "CASCADE")]
public EntitySet<Task> Tasks
{
get { return _tasks; }
set { _tasks.Assign(value); }
}
public TaskPin()
{
_tasks = new EntitySet<Task>(new Action<Task>(this.addTask)
,new Action<Task>(this.removeTask));
}
private void addTask(Task task)
{
NotifyPropertyChanging("Task");
task.Pin = this;
}
private void removeTask(Task task)
{
NotifyPropertyChanging("Task");
task.Pin = null;
}
}
[Table]
public class Task : ModelBase
{
private int _taskId;
[Column(IsPrimaryKey = true, IsDbGenerated = true
,DbType = "INT NOT NULL Identity"
,CanBeNull = false, AutoSync = AutoSync.OnInsert)]
public int TaskId
{
get { return _taskId; }
set { SetProperty(ref _taskId, value); }
}
[Column]
internal int _pinId;
private EntityRef<Pin> _pin;
[Association(Storage = "_pin", ThisKey = "_pinId"
,OtherKey = "PinId"
,IsForeignKey = true
,DeleteOnNull=true)]
public Pin Pin
{
get { return _pin.Entity; }
set
{
if (SetProperty(ref _pin, value) != null)
{
_pinId = value.PinId;
}
}
}
public Task()
{
}
}
I create a TaskPin
and assign it to a board. Then I create two Tasks and assign them to the TaskPin. This does works fine. The problem occurrs when I try to the one or more Tasks
from the TaskPin
:
private void OnDeleteTasks(object sender, EventArgs e)
{
TaskPin taskPin = pin as TaskPin;
var completedTasks = taskPin.Tasks
.Where(x => x.IsDone == true)
.ToList();
foreach (var task in completedTasks)
{
taskPin.Tasks.Remove(task);
}
}
If I call then SubmitChanges()
on my DataContext
object, it will set the Board property
of the TaskPin (inherited from Pin) to null
.
public void Save(Pin pin)
{
// This is empty so no modified members are identified => Correct
var modifiedMembers = db.Pins.GetModifiedMembers(pin);
// Contains just one entry for the deleted Task entity => Correct
var changeSet = db.GetChangeSet();
// This call will immediately set Board property of Pin to null => Wrong!
db.SubmitChanges();
}
I expect that the Task
will be deleted because DeleteOnNull
is set to true but I don't know why the Board property
of Pin is also set to null
which will result in a NullPointerExceptio
or that the Pin is also deleted.
I did a google search on this topic but I don't find anything which solved my problem. An Alternative would be to prevent the nulling of the Board property and call DeleteOnSubmit()
for Task manually.