Develop Reference

C# entity framework 5 set a property only in create

I have a model with a property called "datetime_inclusion" and I need to set a value for this ONLY when I save the first time, there is a way to do this treatment in the model?
I use C# MVC5 and entity framework 5

When you save the first time your object won't have an ID until it gets put into the DB. You can check against this to set your value.
if(myEntity.ObjectID <= 0)
{
myEntity.DateAdded = DateTime.Now;
}

Shoe's answer is perfect. But if you are worry that property can be change in edit time, control that. In create action use Shoe's code and in Edit action use:
[HttpPost]
public ActionResult Edit(int id, Model model)
{
using (var db = new YourEntities())
{
//control that, it does not change
model.datetime_inclusion = db.YourTable.Find(id).datetime_inclusion;
db.Entry(model).State = System.Data.EntityState.Modified;
db.SaveChanges();
return RedirectToAction("Index");
}
}

Not able to retrieve OriginalValues in Entity Framework 5

I am writing a asp.net mvc4 app and I am using entity framework 5. Each of my entities have fields like EnteredBy, EnteredOn, LastModifiedBy and LastModifiedOn.
I am trying to auto-save them by using the SavingChanges event. The code below has been put together from numerous blogs, SO answeres etc.
public partial class myEntities : DbContext
{
public myEntities()
{
var ctx = ((IObjectContextAdapter)this).ObjectContext;
ctx.SavingChanges += new EventHandler(context_SavingChanges);
}
private void context_SavingChanges(object sender, EventArgs e)
{
ChangeTracker.DetectChanges();
foreach (ObjectStateEntry entry in
((ObjectContext)sender).ObjectStateManager
.GetObjectStateEntries
(EntityState.Added | EntityState.Modified))
{
if (!entry.IsRelationship)
{
CurrentValueRecord entryValues = entry.CurrentValues;
if (entryValues.GetOrdinal("LastModifiedBy") > 0)
{
HttpContext currContext = HttpContext.Current;
string userName = "";
DateTime now = DateTime.Now;
if (currContext.User.Identity.IsAuthenticated)
{
if (currContext.Session["userId"] != null)
{
userName = (string)currContext.Session["userName"];
}
else
{
userName = currContext.User.Identity.Name;
}
}
entryValues.SetString(
entryValues.GetOrdinal("LastModifiedBy"), userName);
entryValues.SetDateTime(
entryValues.GetOrdinal("LastModifiedOn"), now);
if (entry.State == EntityState.Added)
{
entryValues.SetString(
entryValues.GetOrdinal("EnteredBy"), userName);
entryValues.SetDateTime(
entryValues.GetOrdinal("EnteredOn"), now);
}
else
{
string enteredBy =
entry.OriginalValues.GetString(entryValues.GetOrdinal("EnteredBy"));
DateTime enteredOn =
entry.OriginalValues.GetDateTime(entryValues.GetOrdinal("EnteredOn"));
entryValues.SetString(
entryValues.GetOrdinal("EnteredBy"),enteredBy);
entryValues.SetDateTime(
entryValues.GetOrdinal("EnteredOn"), enteredOn);
}
}
}
}
}
}
My problem is that entry.OriginalValues.GetString(entryValues.GetOrdinal("EnteredBy")) and entry.OriginalValues.GetDateTime(entryValues.GetOrdinal("EnteredOn")) are not returning the original values but rather the current values which is null. I tested with other fields in the entity and they are returning the current value which were entered in the html form.
How do I get the original value here?

I think the problem may be that you are using the instance provided by the model binder as the input to your controller method, so EF does not know anything about that entity and its original state. Your code may look like this:
public Review Update(Review review)
{
_db.Entry(review).State = EntityState.Modified;
_db.SaveChanges();
return review;
}
In that case, EF knows nothing about the Review instance that is being saved. It is trusting you and setting it as modified, so it will save all of its properties to the database, but it does not know the original state\values of that entity.
Check the section named Entity States and the Attach and SaveChanges Methods of this tutorial. You can also check the first part of this article, that shows how EF does not know about the original values and will update all properties in the database.
As EF will need to know about the original properties, you may first load your entity from the database and then update its properties with the values received in the controller. Something like this:
public Review Update(Review review)
{
var reviewToSave = _db.Reviews.SingleOrDefault(r => r.Id == review.Id);
//Copy properties from entity received in controller to entity retrieved from the database
reviewToSave.Property1 = review.Property1;
reviewToSave.Property2 = review.Property2;
...
_db.SaveChanges();
return review;
}
This has the advantage that only modified properties will be send and updated in the database and that your views and view models don't need to expose every field in your business objects, only those that can be updated by the users. (Opening the door for having different classes for viewModels and models\business objects). The obvious disadvantage is that you will incur an additional hit to the database.
Another option mentioned in the tutorial I referenced above is for you to save the original values somehow (hidden fields, session, etc) and on save use the original values to attach the entity to the database context as unmodified. Then update that entity with the edited fields. However I would not recommend this approach unless you really need to avoid that additional database hit.
Hope that helps!

I was running into a similar problem when trying to audit log the Modified values of an Entity.
It turns out during the post back the ModelBinder doesn't have access to the original values so the Model received is lacking the correct information. I fixed my problem by using this function which clones the current values, relods the object, and then reset the current values.
void SetCorrectOriginalValues(DbEntityEntry Modified)
{
var values = Modified.CurrentValues.Clone();
Modified.Reload();
Modified.CurrentValues.SetValues(values);
Modified.State = EntityState.Modified;
}
You can gain access to the DbEntityEntry though the change tracker, or the entry function from your context.

Update custom user profile fields with SimpleMembershipProvider?

I added a custom field to the UserProfile table named ClassOfYear and I'm able to get the data into the profile during registration like this:
var confirmationToken = WebSecurity.CreateUserAndAccount(model.UserName,
model.Password,
propertyValues: new { ClassOfYear = model.ClassOfYear },
requireConfirmationToken: true);
However, now I want to be able to update the profile when I manage it but I can't seem to find a method to do so. Do I need to simply update the UserProfile table myself? If not, what is the appropriate way of doing this?
FYI, I'm using Dapper as my data access layer, just in case it matters. But, like stated, I can just update the UserProfile table via Dapper if that's what I'm supposed to do, I just figured that the WebSecurity class, or something similar, had a way already since the custom user profile fields are integrated with the CreateUserAndAccount method.
Thanks all!

There is nothing in the SimpleMembershipProvider code that does anything with additional fields except upon create.
Simply query the values yourself from your ORM.
You can use the WebSecurity.GetUserId(User.Identity.Name) to get the user's id and then Dapper to query the UserProfile table.

Just in case anyone facing the same problem. After fighting a lot with the SimpleMembership I got a solution that populates both the webpages_Membership and my custom Users table. For clarification follow my code:
public ActionResult Register(RegisterModel model)
{
if (ModelState.IsValid)
{
TUsuario userDTO= new TUSer()
{
Name = model.Name,
Login = model.Login,
Pass = model.Pass.ToString(CultureInfo.InvariantCulture),
Active = true,
IdCompany = model.IdCompany,
IdUserGroup = model.IdUserGroup,
};
try
{
WebSecurity.CreateUserAndAccount(model.Login, model.Pass, new { IdUser = new UserDAL().Seq.NextVal(), Name = userDTO.Name, Login = userDTO.Login, Active = userDTO.Active, Pass = userDTO.Pass, IdCompany = userDTO.IdCompany, IdUserGroup = userDTO.IdUserGroup });
WebSecurity.Login(model.Login, model.Pass);
After cursing the framework a lot, that gave me a bliss of fresh air :)
PS.: The users table is specified in the global.asax file using the WebSecurity.InitializeDatabaseConnection functon.

Capturing old values for model in MVC3?

I'm wanting to capture the old values within a model so I can compare with the new values after submission, and create audit logs of changes a user makes.
My guess is doing it with hidden input boxes with duplicated old value properties would be one way. But wondering if there are any other good alternatives?
Thanks

In the save method, just go and get the original object from the database before saving the changes, then you have your old and new values to compare against? :)

This sounds like standard auditing. You should not worry about what has changed just capture EVERYTHING and who made the change. Unless there is some sort of real time reporting that needs to be done.
Possible auditing implementations:
CQRS, in a nutshell it tracks every change to a given object. The downside is it's an architecture that is more involved to implement.
The Rolling ledger. Each insert is a new row in the database. The most current row is used for display purposes, but with each update, a new row is inserted into the database.
Yet another approach is to save it off into an audit table.
All get the job done.

You could also store the original model in the view bag and do something like this...
// In the controller
public ActionResult DoStuff()
{
// get your model
ViewBag.OriginalModel = YourModel;
return View(YourModel);
}
// In the View
<input type="hidden" name="originalModel" value="#Html.Raw(Json.Encode(ViewBag.OriginalModel));" />
// In the controller's post...
[HttpPost]
public ActionResult DoStuff(YourModel yourModel, string originalModel)
{
// yourModel will be the posted data.
JavaScriptSerializer JSS = new JavaScriptSerializer();
YourModel origModel = JSS.Deserialize<YourModel>(originalModel);
}
I didn't get a chance to test this, just a theory :)

Exactly what mattytommo says is the preferred method all around
Instantiate new view model for creating a new entity
public ActionResult Edit(int id) {
var entity = new Entity(id); // have a constructor in your entity that will populate itself and return the instance of what is in the db
// map entity to ViewModel using whatever means you use
var model = new YourViewModel();
return View(model);
}
Post changes back
[HttpPost]
public ActionResult Edit(YourViewModel model) {
if (ModelState.IsValid) {
var entity = new YourEntity(model.ID); // re-get from db
// make your comparison here
if(model.LastUserID != entity.LastUserID // do whatever
... etc...
}
return View(model);
}

Multiple instances of IEntityChangeTracker Error

I've read through at least a dozen other questions just like this one, but I am having trouble grasping some of this stuff.
I'm used to developing ASP.NET MVC3 with repositories and code-first entities linking to the entity framework.
I've recently switched to database-first ADO.NET with services development.
I find this to be very clean since I can access stuff through my foreign keys.
Anyway, my old save methods seem to be broken since I constantly get this error
An entity object cannot be referenced by multiple instances of
IEntityChangeTracker
So here's a look at my save action and my service:
Action:
[HttpPost]
public ActionResult AddReview(Review review, int id)
{
User loggedInUser = userService.GetUserByusername(User.Identity.Name);
review.WriterId = loggedInUser.UserId;
review.ProductId = id;
if (ModelState.IsValid)
{
reviewService.Save(review);
Product product = productService.GetProduct(id);
if(product.Quantity>=1)
product.Quantity--;
product.TimesBought++;
productService.UpdateRating(product, reviewService);
loggedInUser.GoldCoins -= product.Price;
Session["goldCoins"] = loggedInUser.GoldCoins;
userService.Save(loggedInUser);
productService.Save(product);
}
else
{
return View(review);
}
return RedirectToAction("Index", "Answers", new { reviewId = review.ReviewId });
Service:
public class ReviewService : Service<Review, CapstoneEntities>
{
...
public void Save(Review review)
{
using (var db = new CapstoneEntities())
{
if (review.ReviewId == 0)
{
db.Reviews.Add(review);
db.Entry(review).State = EntityState.Added;
}
else
{
db.Entry(review).State = EntityState.Modified;
}
db.SaveChanges();
}
}
}
My suspicion is with this line of code: using (var db = new CapstoneEntities()) but I'm not sure how else to do this. Again, this worked perfectly with my old way of doing things but now I get errors on just about ever CRUD operation.
Thank you.

It looks like this is being caused by having an entity belong to multiple DataContexts. Whatever code that is calling that action should use the same DataContext to create the entity as the one used to persist it to the datastore.
In most instances you should only keep one instance of the DataContext. You can use a DI framework like Castle to define/store a dependency (in this case the DataContext) as Transient or PerWebRequest and inject it into the service and controller, so you'll always have a reference to the same instance of the DataContext.

I am new to MVC & Entity frame work. I got same problem after fighting a lot
This solution worked for me. Hope it can be useful for you guys.
var mediaItem = db.MediaItems.FirstOrDefault(x => x.Id == mediaItemViewModel.Id);
mediaItem.Name = mediaItemViewModel.Name;
mediaItem.Description = mediaItemViewModel.Description;
mediaItem.ModifiedDate = DateTime.Now;
mediaItem.FileName = mediaItem.FileName;
mediaItem.Size = KBToMBConversion(mediaItemViewModel.Size);
mediaItem.Type = mediaItem.Type;
//db.Entry(mediaItem).State = EntityState.Modified;// coment This line
db.SaveChanges();
Cause you are reading the the whole object from db and holding it in the current context and when you try to modify the entity state its tells you already one entity attached to the current context. just call save changes it will save it.