/// <summary>
/// Traverse an object graph to populate null reference properties.
/// </summary>
/// <param name="context">Used to query and save changes to a database</param>
/// <param name="item">Object that implements IHasTrackingState</param>
public static void LoadRelatedEntities(this DbContext context, IHasTrackingState item)
{
context.TraverseGraph(item, n =>
{
if (n.Entry.State == EntityState.Detached)
{
n.Entry.State = EntityState.Unchanged;
}
foreach (var reference in n.Entry.References)
{
if (!reference.IsLoaded)
{
reference.Load();
}
}
});
}
/// <summary>
/// Traverse an object graph asynchronously to populate null reference properties.
/// </summary>
/// <param name="context">Used to query and save changes to a database</param>
/// <param name="item">Object that implements IHasTrackingState</param>
public static async Task LoadRelatedEntitiesAsync(this DbContext context, IHasTrackingState item)
{
await context.TraverseGraphAsync(item, async n =>
{
if (n.Entry.State == EntityState.Detached)
{
n.Entry.State = EntityState.Unchanged;
}
foreach (var reference in n.Entry.References)
{
if (!reference.IsLoaded)
{
await reference.LoadAsync();
}
}
});
}
public void ApplyChanges(IHasTrackingState root)
{
ChangeTracker.TrackGraph(root, node =>
{
if (!(node.Entry.Entity is IHasTrackingState hasTrackingState))
{
return;
}
node.Entry.State = EntityState.Detached;
// Get related parent entity
if (node.SourceEntry != null)
{
var relationship = node.InboundNavigation?.GetRelationshipType();
switch (relationship)
{
case RelationshipType.OneToOne:
if (node.SourceEntry.State == EntityState.Added)
{
node.Entry.State = TrackingState.Added.ToEntityState();
}
else if (node.SourceEntry.State == EntityState.Deleted)
{
node.Entry.State = TrackingState.Deleted.ToEntityState();
}
else
{
node.Entry.State = hasTrackingState.TrackingState.ToEntityState();
}
return;
case RelationshipType.ManyToOne:
if (node.SourceEntry.State == EntityState.Added)
{
node.Entry.State = TrackingState.Added.ToEntityState();
return;
}
var parent = node.SourceEntry.Entity as IHasTrackingState;
if (node.SourceEntry.State == EntityState.Deleted ||
parent?.TrackingState == TrackingState.Deleted)
{
try
{
node.Entry.State = TrackingState.Deleted.ToEntityState();
}
catch (InvalidOperationException e)
{
throw new InvalidOperationException(
@"An entity may not be marked as Deleted if it has related entities which are marked as Added.
Remove added related entities before deleting a parent entity.",
e);
}
return;
}
break;
case RelationshipType.OneToMany:
// If ITrackedEntity is set deleted set entity state to unchanged,
// since it may be related to other entities.
if (hasTrackingState.TrackingState == TrackingState.Deleted)
{
node.Entry.State = TrackingState.Unchanged.ToEntityState();
return;
}
break;
}
}
node.Entry.State = hasTrackingState.TrackingState.ToEntityState();
});
/// <summary>
/// Set entity state to Detached for entities in an object graph.
/// </summary>
/// <param name="context">Used to query and save changes to a database</param>
/// <param name="item">Object that implements IHasTrackingState</param>
public static void DetachEntities(this DbContext context, IHasTrackingState item)
{
context.TraverseGraph(item, n => n.Entry.State = EntityState.Detached);
}
