Looking forward to build a framework, (No repository pattern to working with DbSets directly) to autopopulate Created and last modified automatically, rather than spitting out these codes through out code base.
Could you point me out in right direction how to achieve it.
In past I tried populating these in constructors, however that seems
like a nasty code and every time we pull up somting from database EF
change tracking will mark the entity as modified.
.ctor()
{
Created = DateTime.Now;
LastModified = DateTime.Now;
}
public interface IHasCreationLastModified
{
DateTime Created { get; set; }
DateTime? LastModified { get; set; }
}
public class Account : IEntity, IHasCreationLastModified
{
public long Id { get; set; }
public DateTime Created { get; set; }
public DateTime? LastModified { get; set; }
public virtual IdentityUser IdentityUser { get; set; }
}
Starting with v2.1, EF Core provides State change events:
New Tracked And StateChanged events on ChangeTracker can be used to write logic that reacts to entities entering the DbContext or changing their state.
You can subscribe to these events from inside your DbContext constructor
ChangeTracker.Tracked += OnEntityTracked;
ChangeTracker.StateChanged += OnEntityStateChanged;
and do something like this:
void OnEntityTracked(object sender, EntityTrackedEventArgs e)
{
if (!e.FromQuery && e.Entry.State == EntityState.Added && e.Entry.Entity is IHasCreationLastModified entity)
entity.Created = DateTime.Now;
}
void OnEntityStateChanged(object sender, EntityStateChangedEventArgs e)
{
if (e.NewState == EntityState.Modified && e.Entry.Entity is IHasCreationLastModified entity)
entity.LastModified = DateTime.Now;
}
One possible solution (the one we're currently using where I work) is to override the SaveChanges() method in the DbContext and add a little bit of code to loop through changed entities setting the values
public override int SaveChanges()
{
var changedEntriesCopy = ChangeTracker.Entries()
.Where(e => e.State == EntityState.Added ||
e.State == EntityState.Modified ||
e.State == EntityState.Deleted)
.ToList();
var saveTime = DateTime.Now;
foreach (var entityEntry in changedEntriesCopy)
{
if (entityEntry.Metadata.FindProperty("Created") != null && entityEntry.Property("Created").CurrentValue == null)
{
entityEntry.Property("Created").CurrentValue = saveTime;
}
if (entityEntry.Metadata.FindProperty("Updated") != null)
{
entityEntry.Property("Updated").CurrentValue = saveTime;
}
}
return base.SaveChanges();
}
Our situation is basically set up similar to that - Created in our situation is nullable so that when a new entity is created the value is null in code up to creation (makes it easy to check if Created has been populated ever).
There may be other solutions, but this was the easiest to get set up for us, and hasnt had any noticeable performance impact
I'm trying to save an object graph of POCOs I have mapped to EF6 using Code First fluent notations.
Upon saving the object graph however, I stumble upon primary key violation exceptions.
The object graph is quite simple:
One Issue can contain multiple WorkItems with each one Author (as User).
The objects are populated externally (using a Web API)
When I attempt to save an issue with two workitems which refer to the same author, I would expect the issue to be inserted, the workitems to be inserted and one author to be inserted, and the other one to be referenced or be updated.
What happens however is that the issue is inserted, the workitems are inserted and both references to the same user are inserted, resulting in a primary key violation.
Simplified Issue object:
public class Issue
{
public Issue()
{
WorkItems = new List<WorkItem>();
}
public string Id { get; set; }
private List<WorkItem> _workItems;
public List<WorkItem> WorkItems
{
get { return _workItems ?? new List<WorkItem>(); }
set { _workItems = value; }
}
}
Simplified WorkItem:
public class WorkItem
{
public string Id { get; set; }
public string AuthorLogin
{
get; set;
}
private WorkItemAuthor _author;
public WorkItemAuthor Author
{
get { return _author; }
set { _author = value;
if (value != null)
{
AuthorLogin = value.Login;
}
else
{
AuthorLogin = string.Empty;
}
}
}
}
Simplified user object:
public class User
{
public string Login { get; set; }
public string FullName { get; set; }
}
Their Code-first configurations:
internal IssueConfiguration()
{
HasKey(x => x.Id);
HasMany(x => x.WorkItems);
}
internal WorkItemConfiguration()
{
HasKey(x => x.Id);
HasRequired(p => p.Author)
.WithMany(b => b.WorkItems)
.HasForeignKey(x=>x.AuthorLogin);
}
internal UsersConfiguration()
{
HasKey(x => x.Login);
}
All quite straightforward. Upon database create, de tables look fine and dandy too, with FKs on the columns where one would expect them
Now when saving the issue, it would have been nice if the object graph would be inserted, and the reference to existing objects would be recognized automagically and optionally inserted or referenced only.
I attempt to add issues accordingly:
using (var db = new Cache.Context())
{
if (db.Issues.Any(e => e.Id == issue.Id))
{
db.Issues.Attach(issue);
db.Entry(issue).State = EntityState.Modified;
}
else
{
db.Issues.Add(issue);
}
db.SaveChanges();
}
Is the solution to this issue that I walk through the object graph to manually add or attach the other objects in the graph too? I would expect by defining the proper Foreign Key values these references would be recognized.
I finally ended up doing something similar to this, quite laborious and I would still like to find a better way.
Finding out whether an entity is already attached or exists in the database turned out to be pollute the model too much (implementing IEquatable<T> is fine, but I think implementing IEntityWithKey on my POCOs pollutes the POCO too much. (and till that did not seem to suffice tracking entities in the context)
internal static void Save(this List<Issue> issues)
{
using (var db = new Context())
{
foreach (var issue in issues.ToList())
{
foreach (var workItem in issue.WorkItems.ToList())
{
if (workItem.Author != null)
{
var existing = db.Users.SingleOrDefault(e => e.Login == workItem.Author.Login);
if (existing == null)
{
db.Users.Add(workItem.Author);
}
else
{
//Update existing entities' properties
existing.Url = workItem.Author.Url;
//Replace reference
workItem.Author = existing;
}
db.SaveChanges();
}
var existingWorkItem = db.WorkItems.SingleOrDefault(e => e.Id == workItem.Id);
if (existingWorkItem == null)
{
db.WorkItems.Add(workItem);
}
else
{
//Update existing entities' properties
existingWorkItem.Duration = workItem.Duration;
//Replace reference
issue.WorkItems.Remove(workItem);
issue.WorkItems.Add(existingWorkItem);
}
db.SaveChanges();
}
var existingIssue = db.Issues.SingleOrDefault(x => x.Id == issue.Id);
if (existingIssue == null)
{
db.Issues.Add(issue);
}
else
{
//Update existing entities' properties
existingIssue.SpentTime = issue.SpentTime;
}
db.SaveChanges();
}
}
}
There is a small bug in the Issue object.
"return _workItems ?? new List();" could return a new WorkItem on every get if _workItems ever became null. Here is the fixed version.
public class Issue {
public Issue() {
WorkItems = new List<WorkItem>();
}
public String Id {
get; set;
}
public List<WorkItem> WorkItems { get; private set; }
}
Frustrating, this. Here's a pair of related objects, as generated by database-first Entity Framework:
public partial class DevelopmentType
{
public DevelopmentType()
{
this.DefaultCharges = new HashSet<DefaultCharge>();
}
public System.Guid RowId { get; set; }
public string Type { get; set; }
public virtual ICollection<DefaultCharge> DefaultCharges { get; set; }
}
public partial class DefaultCharge
{
public System.Guid RowId { get; set; }
public decimal ChargeableRate { get; set; }
public Nullable<System.Guid> DevelopmentType_RowId { get; set; }
public virtual DevelopmentType DevelopmentType { get; set; }
}
Here's the code that I'm calling to save a DevelopmentType - it involves automapper since we differentiate entity objects from DTOs:
public void SaveDevelopmentType(DevelopmentType_dto dt)
{
Entities.DevelopmentType mappedDevType = Mapper.Map<DevelopmentType_dto, Entities.DevelopmentType>(dt);
_Context.Entry(mappedDevType).State = System.Data.EntityState.Modified;
_Context.DevelopmentTypes.Attach(mappedDevType);
_Context.SaveChanges();
}
In my user interface, the most common operation will be for a user to look at a list of DevelopmentTypes and update their DefaultCharge. So when I test this using the above code, it runs without error, but nothing actually changes.
If I pause in the debugger it's clear that the changed DefaultCharge is being passed into the function, and that it's attached to the DevelopmentType to be saved.
Stepping through it, if I change the value manually inside visual studio, it does save the updated value. Which is just even more confusing.
Monitoring the database with SQL Server Profiler reveals that update commands are issued only for the parent object and not for any attached objects.
I have other similar code elsewhere that functions as expected. What am I doing wrong here?
EDIT:
I have discovered that if you do this prior to the call to SaveDevelopmentType:
using (TransactionScope scope = new TransactionScope())
{
dt.Type = "Test1";
dt.DefaultCharges.First().ChargeableRate = 99;
_CILRepository.SaveDevelopmentType(dt);
scope.Complete();
}
The change to Type saves, but the change to ChargeableRate does not. I don't think it helps, massively, but thought I'd add it.
The problem is, that EF is not aware of the changed DefaultCharges.
By setting the State of the DevelopmentType to EntityState.Modified, EF only knows that the object DevelopmentType has been changed. However, this means that EF will only update DevelopmentType but not it's navigation properties.
A workaround - which isn't best practice - would be to iterate over all DefaultCharge of the current DevelopmentType and set the entity state to EntityState.Modified.
Additionally I would recommend to attach the entity to the context first, and change the state afterwards.
EDIT after comment
As you are using DTOs I suppose you are transfering these objects either through different layers or different machines.
In this case I would recommend to use self tracking entities, because it is not possible to share one context. These entities additionally holds their current state (ie. new, updated, deleted etc). There are many tutorials on the net about self tracking entities.
e.g. MSDN - Working with Self-Tracking Entities
As far as I know EF can save child entities only if the parent object was retrieved with the same Context that is trying to save it. That is attaching an object that was retrieved by one context to another context, will allow you to save changes to parent objects but not children. This was the result of a on old search based on which we switched to NHibernate. If memory serves correctly I was able to find a link where EF team member(s) confirmed this and that there WAS no plan to change this behavior. Unfortunately all links related to that search have been erased from my PC since.
As I am not aware of how you are retrieving the objects in your case, I am not sure this is relevant to your case, but put it out there just in case it helps.
Here is a link on attaching detached objects to a context.
http://www.codeproject.com/Articles/576330/Attaching-detached-POCO-to-EF-DbContext-simple-and
Context.Entry() already "Attaches" the Entity internally in order to have the context change its EntityState.
By calling Attach() you're changing the EntityState back to Unchanged. Try to comment out this line.
The Graphdiff library was a great help for me to handle all of these complexities.
You only need to set up the navigation properties that you wish to insert/update/delete (using fluent syntax) and Graphdiff will take care of it
Note: It seems to be that the project is not updated anymore but i'm using it since more than a year and is quite stable
This is not a workaround for every case, but I did discover that you can get around this by updating foreign keys on an object instead of updating navigation property objects.
For example... instead of:
myObject.myProperty = anotherPropertyObject;
Try this:
myObject.myPropertyID = anotherPropertyObject.ID;
Make sure the object is flagged as modified in EF's mind (as mentioned in other posts) and then call your save method.
Worked for me at least! It'll be a no-go when working with nested properties, but perhaps you can break your contexts up into smaller chunks and work over objects in multiple parts to avoid context bloat.
Good luck! :)
If I understand the question correctly, you have problem updating child fields. I had problems with child collection fields. I tried this and it worked for me.
You should update all child collections after attaching the object to the database context change the modified state of the parent object and save changes to the context.
Database.Products.Attach(argProduct);
argProduct.Categories = Database.Categories.Where(x => ListCategories.Contains(x.CategoryId)).ToList();
Database.Entry(argProduct).State = EntityState.Modified;
Database.SaveChanges();
I created a helper method to solve this problem.
Consider this:
public abstract class BaseEntity
{
/// <summary>
/// The unique identifier for this BaseEntity.
/// </summary>
[Key]
public Guid Id { get; set; }
}
public class BaseEntityComparer : IEqualityComparer<BaseEntity>
{
public bool Equals(BaseEntity left, BaseEntity right)
{
if (ReferenceEquals(null, right)) { return false; }
return ReferenceEquals(left, right) || left.Id.Equals(right.Id);
}
public int GetHashCode(BaseEntity obj)
{
return obj.Id.GetHashCode();
}
}
public class Event : BaseEntity
{
[Required(AllowEmptyStrings = false)]
[StringLength(256)]
public string Name { get; set; }
public HashSet<Manager> Managers { get; set; }
}
public class Manager : BaseEntity
{
[Required(AllowEmptyStrings = false)]
[StringLength(256)]
public string Name { get; set; }
public Event Event{ get; set; }
}
DbContext with the helper method:
public class MyDataContext : DbContext
{
public MyDataContext() : base("ConnectionName") { }
//Tables
public DbSet<Event> Events { get; set; }
public DbSet<Manager> Managers { get; set; }
public async Task AddOrUpdate<T>(T entity, params string[] ignoreProperties) where T : BaseEntity
{
if (entity == null || Entry(entity).State == EntityState.Added || Entry(entity).State == EntityState.Modified) { return; }
var state = await Set<T>().AnyAsync(x => x.Id == entity.Id) ? EntityState.Modified : EntityState.Added;
Entry(entity).State = state;
var type = typeof(T);
RelationshipManager relationship;
var stateManager = ((IObjectContextAdapter)this).ObjectContext.ObjectStateManager;
if (stateManager.TryGetRelationshipManager(entity, out relationship))
{
foreach (var end in relationship.GetAllRelatedEnds())
{
var isForeignKey = end.GetType().GetProperty("IsForeignKey", BindingFlags.Instance | BindingFlags.NonPublic)?.GetValue(end) as bool?;
var navigationProperty = end.GetType().GetProperty("NavigationProperty", BindingFlags.Instance | BindingFlags.NonPublic)?.GetValue(end);
var propertyName = navigationProperty?.GetType().GetProperty("Identity", BindingFlags.Instance | BindingFlags.NonPublic)?.GetValue(navigationProperty) as string;
if (string.IsNullOrWhiteSpace(propertyName) || ignoreProperties.Contains(propertyName)) { continue; }
var property = type.GetProperty(propertyName);
if (property == null) { continue; }
if (end is IEnumerable) { await UpdateChildrenInternal(entity, property, isForeignKey == true); }
else { await AddOrUpdateInternal(entity, property, ignoreProperties); }
}
}
if (state == EntityState.Modified)
{
Entry(entity).OriginalValues.SetValues(await Entry(entity).GetDatabaseValuesAsync());
Entry(entity).State = GetChangedProperties(Entry(entity)).Any() ? state : EntityState.Unchanged;
}
}
private async Task AddOrUpdateInternal<T>(T entity, PropertyInfo property, params string[] ignoreProperties)
{
var method = typeof(EasementDataContext).GetMethod("AddOrUpdate");
var generic = method.MakeGenericMethod(property.PropertyType);
await (Task)generic.Invoke(this, new[] { property.GetValue(entity), ignoreProperties });
}
private async Task UpdateChildrenInternal<T>(T entity, PropertyInfo property, bool isForeignKey)
{
var type = typeof(T);
var method = isForeignKey ? typeof(EasementDataContext).GetMethod("UpdateForeignChildren") : typeof(EasementDataContext).GetMethod("UpdateChildren");
var objType = property.PropertyType.GetGenericArguments()[0];
var enumerable = typeof(IEnumerable<>).MakeGenericType(objType);
var param = Expression.Parameter(type, "x");
var body = Expression.Property(param, property);
var lambda = Expression.Lambda(Expression.Convert(body, enumerable), property.Name, new[] { param });
var generic = method.MakeGenericMethod(type, objType);
await (Task)generic.Invoke(this, new object[] { entity, lambda, null });
}
public async Task UpdateForeignChildren<T, TProperty>(T parent, Expression<Func<T, IEnumerable<TProperty>>> childSelector, IEqualityComparer<TProperty> comparer = null) where T : BaseEntity where TProperty : BaseEntity
{
var children = (childSelector.Invoke(parent) ?? Enumerable.Empty<TProperty>()).ToList();
foreach (var child in children) { await AddOrUpdate(child); }
var existingChildren = await Set<T>().Where(x => x.Id == parent.Id).SelectMany(childSelector).AsNoTracking().ToListAsync();
if (comparer == null) { comparer = new BaseEntityComparer(); }
foreach (var child in existingChildren.Except(children, comparer)) { Entry(child).State = EntityState.Deleted; }
}
public async Task UpdateChildren<T, TProperty>(T parent, Expression<Func<T, IEnumerable<TProperty>>> childSelector, IEqualityComparer<TProperty> comparer = null) where T : BaseEntity where TProperty : BaseEntity
{
var stateManager = ((IObjectContextAdapter)this).ObjectContext.ObjectStateManager;
var currentChildren = childSelector.Invoke(parent) ?? Enumerable.Empty<TProperty>();
var existingChildren = await Set<T>().Where(x => x.Id == parent.Id).SelectMany(childSelector).AsNoTracking().ToListAsync();
if (comparer == null) { comparer = new BaseEntityComparer(); }
var addedChildren = currentChildren.Except(existingChildren, comparer).AsEnumerable();
var deletedChildren = existingChildren.Except(currentChildren, comparer).AsEnumerable();
foreach (var child in currentChildren) { await AddOrUpdate(child); }
foreach (var child in addedChildren) { stateManager.ChangeRelationshipState(parent, child, childSelector.Name, EntityState.Added); }
foreach (var child in deletedChildren)
{
Entry(child).State = EntityState.Unchanged;
stateManager.ChangeRelationshipState(parent, child, childSelector.Name, EntityState.Deleted);
}
}
public static IEnumerable<string> GetChangedProperties(DbEntityEntry dbEntry)
{
var propertyNames = dbEntry.State == EntityState.Added ? dbEntry.CurrentValues.PropertyNames : dbEntry.OriginalValues.PropertyNames;
foreach (var propertyName in propertyNames)
{
if (IsValueChanged(dbEntry, propertyName))
{
yield return propertyName;
}
}
}
private static bool IsValueChanged(DbEntityEntry dbEntry, string propertyName)
{
return !Equals(OriginalValue(dbEntry, propertyName), CurrentValue(dbEntry, propertyName));
}
private static string OriginalValue(DbEntityEntry dbEntry, string propertyName)
{
string originalValue = null;
if (dbEntry.State == EntityState.Modified)
{
originalValue = dbEntry.OriginalValues.GetValue<object>(propertyName) == null
? null
: dbEntry.OriginalValues.GetValue<object>(propertyName).ToString();
}
return originalValue;
}
private static string CurrentValue(DbEntityEntry dbEntry, string propertyName)
{
string newValue;
try
{
newValue = dbEntry.CurrentValues.GetValue<object>(propertyName) == null
? null
: dbEntry.CurrentValues.GetValue<object>(propertyName).ToString();
}
catch (InvalidOperationException) // It will be invalid operation when its in deleted state. in that case, new value should be null
{
newValue = null;
}
return newValue;
}
}
Then I call it like this
// POST: Admin/Events/Edit/5
[HttpPost]
[ValidateAntiForgeryToken]
public async Task<ActionResult> Edit(Event #event)
{
if (!ModelState.IsValid) { return View(#event); }
await _db.AddOrUpdate(#event);
await _db.SaveChangesAsync();
return RedirectToAction("Index");
}
As part of the save operation in my DbContext, I need to serialize extended information to be stored in a binary field in the database.
I've written the following method to intercept all Client objects that have been added or modified to ensure the serialization takes place before they are saved. I'm wondering if there is a better way of doing this or if there will be problems created by this method.
public int Save()
{
foreach (Client client in this.Context.Local.Clients)
{
EntityState state = this.Context.Entry(client).State;
if (state == EntityState.Added || state == EntityState.Modified)
{
client.SerializeExtended();
}
}
return this.Context.SaveChanges();
}
override DbContext.SaveChanges method.
protected override int SaveChanges()
{
foreach (var entry in ChangeTracker.Entries<Clients())
{
var entity = entry.Entity;
if (entry.State == EntityState.Added || entry.State == EntityState.Modified)
{
entry.Entity.SerializeExtended();
}
}
base.SaveChanges();
}
So basically I'm trying to do this sequence of events in entity framework.
Create a new account
Get an existing account
Move all the data from the old account to the new account (transactions, users, etc)
Delete the old account
I'm doing this all in 'one go', inside a single ObjectContext.
It fails when I call SaveChanges on the context. I get an foreign key constraint error.
I checked this in SQL profiler and it turns out that entity framework isn't sending any of the updates, just the selected and then a delete.
I kinda understand WHY it is working like that but there must be some way to force it do work properly, without having to call SaveChanges() twice or something.
Hopefully.
My merge function basically looks like this
public void Merge(Account newAccount, Account oldAccount)
{
// ...
foreach (var user in oldAccount.Users.ToList())
{
oldAccount.Users.Remove(user);
newAccount.Users.Add(user);
}
// ...
_unitOfWork.Accounts.Delete(oldAccount);
}
The objects are POCO objects created by the E.F.4 POCO Entity Generator. To avoid pasting the entire class here's just one of the association properties with it's 'fixup' function.
public virtual ICollection<User> Users
{
get
{
if (_users == null)
{
var newCollection = new FixupCollection<User>();
newCollection.CollectionChanged += FixupUsers;
_users = newCollection;
}
return _users;
}
set
{
if (!ReferenceEquals(_users, value))
{
var previousValue = _users as FixupCollection<User>;
if (previousValue != null)
{
previousValue.CollectionChanged -= FixupUsers;
}
_users = value;
var newValue = value as FixupCollection<User>;
if (newValue != null)
{
newValue.CollectionChanged += FixupUsers;
}
}
}
}
private void FixupUsers(object sender, NotifyCollectionChangedEventArgs e)
{
if (e.NewItems != null)
{
foreach (User item in e.NewItems)
{
item.Account = this;
}
}
if (e.OldItems != null)
{
foreach (User item in e.OldItems)
{
if (ReferenceEquals(item.Account, this))
{
item.Account = null;
}
}
}
}
You use object as reference to add and remove inside the for loop , the best solution to get object by key instate of using an object when add.
oldAccount.Users.Remove(user);
newAccount.Users.Add(users.FirstOrDefault(t=>t.ID = user.Id));
Okay figured out the solution. #CodeGorilla's comment gave me a hint.
Essentially I just need to call
_context.SaveChanges(SaveOptions.AcceptAllChangesAfterSave);
before trying to delete the account. This forces entity framework to do all the updates in the database. After that there is no problem with deleting it.