I have a code first model with a mapping table so that I can map MenuItem to an IdentityRole, enabling the production of a menu based on the logged in users role assignment.
public class MenuItem
{
public int Id { get; set; }
public string Text { get; set; }
}
public class MenuRoleMap
{
[Key]
public int Id { get; set; }
public virtual MenuItem MenuItem { get; set; }
public virtual IdentityRole Role { get; set; }
}
The IdentityRole and rest of Identity is auto wired via IdentityDbContext which I've inherited through my ApplicationDbContext like this, then the context should be consistent.
public class ApplicationDbContext : IdentityDbContext<User>
All of the tables look right, they have the expected columns and foreign keys, here is the MenuRoleMap table
I have an valid existing instance of MenuItem and IdentityRole which I use to try and add a new entity item to this table
foreach (IdentityRole role in selectedRoles)
{
MenuRoleMap mrm = new MenuRoleMap();
mrm.MenuItem = menuItem;
mrm.Role = role;
db.MenuRoleMaps.Add(mrm);
}
db.SaveChanges(); /// <<<=== HERE ERROR BECAUSE THE role IS ALREADY IN DB
Which throws this error
A first chance exception of type 'System.Data.Entity.Validation.DbEntityValidationException' occurred in EntityFramework.dll
Role: Role SystemsAdministrator already exists.
Which of course, it does exist, I know that, it's already in the database. Surely the EF should not be trying to add a new entity item for the foreign key entity if it already exists?
It doesn't do it for the MenuItem, only the IdentityRole.
I thought the problem was proxy creation since the IdentityRole was a proxy object, so I turned that off
this.Configuration.ProxyCreationEnabled = false;
but I still get the same error.
My question is, how do you add an entity where the foreign key is an IdentityRole?
Thank you stackers.
ANSWER TO MY OWN QUESTION
After assistance from those below I discovered while investigating the various solutions that the problem wasn't one of context per se but the validity of an object. The object looked right, what I hadn't realised is that it wasn't the object from the context, it was a facsimile. By trying to add this facsimile to the model, the context quite rightly says it already exists, you can't add it again. By trying to override the state of the item I created a different kind of error.
The resolution was simply to reload the object from the context and then add that to the parent item like so
foreach (IdentityRole role in selectedRoles)
{
// Here I'm getting the role from the context using the ID I have from the facsimile
IdentityRole roleToUse = db.Roles.Where(x => x.Id == role.Id).FirstOrDefault();
// carry on as normal
MenuRoleMap mrm = new MenuRoleMap();
mrm.MenuItem = menuItem;
mrm.Role = roleToUse; // note I'm using the retrieved 'roleToUse'
db.MenuRoleMaps.Add(mrm);
}
db.SaveChanges();
Hey presto it all works.
It looks like you've retrieved the entity from another context and then assigned it to an entity which is then added to a different context. It would then try to insert the Role entity too.
Are you returning the Role from another method where the lifetime of the context is scoped to that method?
You may find the following link useful in regards to updating the state of objects:
Entity states and SaveChanges
The problem is that when you use db.Set<MyEntity>.Add you will mark all entities that are attached to the entity that is added as being added too. You have to explicitly mark them as being unchanged:
foreach (IdentityRole role in selectedRoles)
{
MenuRoleMap mrm = new MenuRoleMap();
mrm.MenuItem = menuItem;
mrm.Role = role;
db.MenuRoleMaps.Add(mrm);
db.Entry(role).State=EntityState.Unchanged;
}
db.SaveChanges();
My answer is you can't or at least should not.
Authentication (Roles), and Business (Menu) are different concerns of the application.
For me you have to bring in the ApplicationDb, the part of IdentityDb that you need and organize the synchronisation.
To illustrate my saying: Imaging you use Google or LiveID as authentification provider: can you imagine navigation properties from you ApplicationDd to Google or Microsoft Dbs ?
Clearly not.
So create a AppRole replicating the Role of the authentication database and use this table from your application database to build your menus.
In pseudo code this looks like:
List<Int32> l = IdentityContext.GetRolesForUser(currentUserId);
foreach (AppRole role in AppContext.Roles.Where(r => l.Contains(r.Id)))
{
MenuRoleMap mrm = new MenuRoleMap();
mrm.MenuItem = menuItem;
mrm.Role = role;
appContext.MenuRoleMaps.Add(mrm);
}
appContext.SaveChanges();
Another solution would be to use the same context for Application and Identity.
Inheritance of context seems fine, but I never tested it.
Related
So with entity framework I'm trying to update two existing entities.
There I've the main object something like:
public class MainObject
{
public string Name { get; set; }
public virtual SmallObject Part { get; set;}
}
public class SmallObject
{
public string Name { get; set; }
}
In the repository I first check if the SmallObject already exists in the database by:
MainObject.Part = (from s in repoSmallObject.GetAll()
where s.name == MainObject.Part.Name
select s).FirstOrDefault();
Then finally I call the update method in my GenericRepository
repoMainObject.Update(MainObject)
which is defined as a generic repository method:
dbSet.Attach(entity)
context.Entry(entity).State = EntityState.Modified;
context.SaveChanges();
But the relationship doesn't get updated. Why is that? Both objects are attached to context not?
*Edit: The two repo's are injected with the same Context.
And strangely enough the Add method works and also updates the relationship.
When you set
context.Entry(entity).State = EntityState.Modified;
you need at least to set the state after and before updates (i.e. context.Entry(mainObject).CurrentValues and OriginalValues) so EF can build the right UPDATE query (with right WHERE clause).
It works if you set
context.Entry(entity).State = EntityState.Added;
because EF needs just to generate an INSERT query.
I don't know exactly why you need it but usually I prefer to attach the object to the DbSet and modify the properties so EF handles various states.
dbSet.Attach(MainObject)
MainObject.Part = (from s in repoSmallObject.GetAll()
where s.name == MainObject.Part.Name
select s).FirstOrDefault();
(In your case does not work because MainObject.Part.Name does not change)
The attached object should have the same values of the database otherwise you have a concurrency exception.
BTW, why you don't read the old object (MainObject) from the DB than work on it???
I just want to know if there's a way on how to create an Updatable model. Right now, I have to create procedures for insert, update, and delete for all of the tables in my model. This is very tedious so I was wondering if there is one way which I could do to resolve this?
I remember before in my previous work that we used to make models and access them (CRUD) without creating procedures. But i'm not really certain now on how it was made.
Thank you!
There are various ways in which you can automate the generation (on the fly or already generated at compile time) of the actual SQL calls to the database to insert, select, update and delete within the Entity Framework.
You can use the ORM tools (e.g. Linq to Entities) to minimise or eliminate the writing of raw SQL. This means you still have to use the correct attributes on your entities and the properties/methods therein and that's a manual process. (Some backgrounding on this MSDN page)
You can allow the framework to automatically generate your entities based on some existing database schema (only possible with SqlServer-type databases) which basically does 90% of the work for you. There may be some cases where you need to override, for example, the default insert SQL with something custom. This is achieved via the Generate Database Wizard (which I think is a part of Visual Studio 2008+).
You can use POCO classes with EF. If you're using 4.1 and above, you can use the DbContext class. To map your model to the table / columns, simply override OnModelCreating in your context class (which inherits from DbContext). Say you have a model called User, a table called Users, and the context class MyContext, the code could be smth like this:
public class User
{
public int UserId { get; set; }
public string UserName { get; set; }
}
public class MyContext : DbContext
{
public MyContext() :
base("MyContext")
{
}
public DbSet<User> Users { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Entity<User>().
.ToTable("Users");
modelBuilder.Entity<User>().
.Property(d => d.UserId)
.HasColumnName("UserId")
modelBuilder.Entity<User>().
.Property(d => d.UserName)
.HasColumnName("UserName");
}
}
To use it, simply add the User instance to your DbSet, then call SaveChanges:
using(MyContext ctx = new MyContext())
{
var u = new User() { UserId = 1, UserName = "A" };
ctx.Users.Add(u);
ctx.SaveChanges();
}
I have the following tables/views
Users (View)
-> UserId
-> Name
Roles (Table)
-> RoleId
-> Name
UserRoles (Table)
-> UserId
-> RoleId
and the classes
public class Role{
public int RoleId{get;set}
public string Name{get;set}
}
public class User{
public int UserId{get;set}
public string Name{get;set}
public ICollection<Role> Roles{get;set}
}
and the save method
using (var helper = new DbContext())
{
helper.Users.Attach(user);
helper.SaveChanges();
}
As you can see above, the Users is a view and UserRoles is a mapping table. I am able to retrieve User entities along with the mapped Roles. But while saving it is not throwing any exceptions nor is it saving. I tried checking the db using profiler and it is not even hitting the db.
Since Users is a view I don't want to save the User entity but only the changes made in the Roles collection.
This cannot save anything. Attach puts the whole object graph into the context, but in state Unchanged. If all objects in the context are unchanged SaveChanges won't issue any command to the DB (because for EF nothing has changed).
If you want to make changes which EF recognizes as such you must first attach the object which represents the state in the Db and then make your changes, something like:
using (var helper = new DbContext())
{
helper.Users.Attach(user);
helper.Roles.Attach(myNewRole);
user.Name = myNewName;
user.Roles.Add(myNewRole);
// etc.
helper.SaveChanges();
}
Alternatively you can mark the user as modified:
helper.Entry(user).State = EntityState.Modified;
But I believe this only affects scalar properties of the entity and it doesn't solve the problem to add a new role to the user.
I'm using VS2010, EF4 feature CTP (latest release), and POCO objects, such as the example below:
class Person
{
public int ID { get; set; }
public string Name { get; set; }
public virtual IList<Account> Accounts { get; set; }
...
}
class Account
{
public string Number { get; set; }
public int ID { get; set; }
...
}
For the sake of brevity, assume context below is the context object for EF4. I have a dbml mapping between entity types and the database, and I use it like this with no problem:
Person doug = context.Persons.CreateObject();
doug.Name = "Doug";
context.Add(doug);
context.Save();
doug.Accounts.Add(new Account() { Name = "foo" });
context.Save(); // two calls needed, yuck
At this point, the database has a Person record with the name "Doug", and an account record "foo". I can query and get those record back just fine. But if I instead try to add the account before I save the Person, the Accounts list is null (the proxy hasn't created an instance on that property yet). See the next example:
Person doug = context.Persons.CreateObject();
doug.Name = "Doug";
doug.Accounts.Add(new Account() { Name = "foo" }); // throws null reference exception
context.Add(doug);
context.Save();
Has anybody else encountered this? Even better, has anyone found a good solution?
Person doug = context.Persons.CreateObject();
doug.Name = "Doug";
context.Add(doug);
doug.Accounts.Add(new Account() { Name = "foo" });
context.Save();
This will work
Yes and yes!
When you new the POCO up (as opposed to CreateObject from the Context), no proxies are provided for you. This may seem obvious, but I had to explicitly remind myself of this behavior when chasing a similar issue down. (I know this isn't the situation you described in the question, but the overall issue should be acknowledged).
Initializing collections in the constructor of the POCO does not interfere with proper EF4 proxy lazy-loading behavior, from what I've observed in my own testing.
OK, all this being said, I now see your comment to the previous answer -- why don't I have a proxied Addresses collection when I request a new Person from my context? Do you have lazy loading enabled on the context? Seeing how we're dealing with navigation properties, I could see where having lazy loading turned off may make a difference in this situation.
ISTM that if you expect the framework to do all this for you then you wouldn't really have a "POCO", would you? Take your Person class, with the code above. What would you expect the state of the Accounts property to be after construction, with no constructor, if the EF weren't involved? Seems to me that the CLR will guarantee them to be null.
Yes, proxies can initialize this when necessary for materialization of DB values, but in the EF, "POCO" actually means "Plain". Not "something packed with runtime-generated code which we pretend is 'Plain'".
I'm using .NET 3.5 SP1 in ASP.NET MVC application.
While using ObjectContext with Http Request lifetime, and trying to attach an entity ALREADY present in context, we get error:
"An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key."
For Example, the code :
Category newCategory = new Category {CategoryId = CategoryIdSelected};
ctx.AttachTo("CategorySet", newCategory);
will give error if 'Category' with CategoryId = CategoryIdSelected exists in ObjectContext.
Modified code to check for existing entity:
Category newCategory = new Category {CategoryId = CategoryIdSelected};
ObjectStateEntry stateEntry = null;
if( ctx.ObjectStateManager.TryGetObjectStateEntry(newCategory, out stateEntry)){
//EntityObject already attached in context, get it
newCategory = (EntityObject)stateEntry.Entity;
}else{
ctx.AttachTo("CategorySet", newCategory);
}
The modified code is still giving same error:
"[System.InvalidOperationException] = {"An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key."
Please advise ?
Thank You
QUESTION ADDENDUM:
More problems attaching Entities when using ObjectContext having lifetime of Http Request.
For Example, if we have 'AppUser','Category' and Department entities.
public class AppUser : System.Data.Objects.DataClasses.EntityObject{
public int Uid {get; set;}
public string UserName {get; set;}
public string Password {get; set;}
public Department Dept {get; set;}
public Category catg {get; set;}
...........
}
AppUser has relationship with Department and Category Entities.
Now when trying to attach 'user':
user = new AppUser{Uid=1,catg = new Category {categoryId=10}, Dept = new Department{departmentId=101}, ...}
var key = ctx.CreateEntityKey("AppUserSet", user);
if (ctx.ObjectStateManager.TryGetObjectStateEntry(key, out stateEntry)) {
will work ONLY if, in context :
there is NO Category with categoryId=10, and
there is NO Department with departmentId=101
One option, is to ensure context does not have attached entities by always retrieving using NOMERGE NoTracking option. BUT I found following problems with MergeOption.NoTracking:
Second call would still result in db hit
You don't get EntityKeys on EntityRefs. So EntityKey of XXXReference is null,which means NO FK Stub. Please see.
How to get EntityKey of Reference w/o loading both ends (both entities)?
Even though Entity are Detached, they have a reference to the DataContext (via entity._realtionships._context). Please see.
Please advise.
Thank You.
Your code is using two different contexts. You check one, and then attach to the other:
if( csContext. //...){
///
}else{
ctx. // ...
}
The entity appears to be in ctx, but not in csContext. My advice is to use only one context at a time whenever possible; it's much less confusing.
Update
OK, you've changed the code in your question.
My guess is that your stub object doesn't have an EntityKey, so TryGetObjectStateEntry is returning false. Try:
if( ctx.ObjectStateManager.TryGetObjectStateEntry(
new EntityKey("MyEntities.CategorySet", "CategoryId", CategoryIdSelected),
out stateEntry)){
Obviously, replace "MyEntities" with the actual model name.