For some reason I am getting the following error at the db.SaveChanges(); instruction:
Cannot insert the value NULL into column 'UserId', table 'XXXXXXXXX_Dev.dbo.Portfolios'; column does not allow nulls. INSERT fails.
The statement has been terminated.
Controller code:
[HttpPost]
[Authorize]
public ActionResult Create(Portfolio portfolio)
{
if (ModelState.IsValid)
{
portfolio.UserId = (Guid)Membership.GetUser().ProviderUserKey;
db.AddToPortfolios(portfolio);
db.SaveChanges();
}
return View("MyPortfolios");
}
I have stepped through the debugger and confirmed that UserID is being populated.
Update:
I have tried changing db.AddToPortfolios(portfolio); to db.Portfolios.AddObject(portfolio); but it is still having the same problem.
Portfolios is an ObjectSet, should I use the Attach() method?
I know this exception from only one situation, that is: UserId is not an identity column in your database but in the EF model the corresponding property is flagged as such - which means it is either explicitely attributed with DatabaseGeneratedOption.Identity or implicitely by conventions.
The problem is that in this case EF won't sent the property value to the Db (no matter if it's set or not) because it assumes that the DB will do the work to create a column value. But the Db doesn't, hence the exception.
Just a guess.
Edit:
To solve the problem you must flag UserId with DatabaseGeneratedOption.None.
Related
I have following Model class that is used during the Web API Post. As you can see Id field is annotated as Required.
public class Model
{
[Required]
public Guid Id { get; set; }
}
The Post for API is as follows
[HttpPost]
public IActionResult Post([FromBody]Model value)
{
if (!ModelState.IsValid)
return BadRequest();
Model newModel = new Model() { Id = value.Id };
return Ok(newModel);
}
On a sunny day, this is what I see. All good
enter image description here
On a rainy day, when Id is not provided, I get following.
enter image description here
Given that in the second example, a Required field is not provided, shouldn't a BadRequest is returned rather than a 200 with invalid id guid with 00000000-0000-0000-0000-000000000000?
Using the Required annotation
In the Web API Docs, your issue is known as 'under-posting'.
The issue is that Guid has a default value, so when no value is provided, it is initialized with the default value... which then satisfies the Required constraint.
To prevent this, counter-intuitively you make the Guid nullable using Guid?.
Then if the value is not provided, the deserializer will set the value to null, which will cause the Required constraint to be violated.
If the value is provided, it will be set, and all will be well.
See https://www.asp.net/web-api/overview/formats-and-model-binding/model-validation-in-aspnet-web-api for more details, there is an example of a similar issue for a decimal property.
The key distinction to understand is that Guid.Empty is really a valid Guid. The only way to distinguish between the user providing a Guid (which is empty) and not providing one at all is to make it nullable, so null = not provided, and Empty = the user provided the empty Guid.
Using a Custom Annotation
If you really don't want to make your Guid nullable, you need to consider what would you do for a 'normal' value type, e.g. an integer. Rather than making it required, you'd use a Range attribute and specify that it must be > 0.
Similarly for Guids, you'd ideally have an attribute that would simply test that it is != Guid.Empty
See https://learn.microsoft.com/en-us/aspnet/core/mvc/models/validation#custom-validation for guidance on creating a custom validation atribute.
I have done something similar in the past where it updates the table based on an id. Here is the code worked for me in the past but its returning null error.
Object reference not set to an instance of an object. System.NullReferenceException: Object reference not set to an instance of an object.
public ActionResult TestUpdate()
{
int id = 3; // this is the FK which exists on the Transactions table.
var results = db.StoreTransactions.Find(id);
if(results != null)
{
results.TransStatus = "Completed";
db.SaveChanges();
}
}
It appears that results is null but i verified that the record #3 exists. To simply the code below I hard-coded.
I just want to update the results.TransStatus to "Completed".
Can anyone help please. Thank you!
----------------- UPDATE ---------------------
I found out that Find() does not work with foreign keys(FK). I hard-coded PK and its no longer Null.
However, I'm still not able to update the table to completed. How can I update the table or the transStatus field? Is the code correct? Thanks again for your time.
I fixed it. The db.Entry(results).State = EntityState.Modified was missing. I still don't understand how or why the same code worked on my previous project.
I've managed to create number of readonly Web Api OData services following the tutorials here: http://www.asp.net/web-api/overview/odata-support-in-aspnet-web-api. I'm therefore employing the ODataConventionModel builder to create the model from a set of entities (incidentally coming from a Telerik ORM). This all seems to work fine and I can happily issue queries, view the metadata and so forth on the service.
I've now tried to turn my attention to the other CRUD operations - firstly Create and have stumbled into a problem! Namely, the Post method fires correctly (CreateEntity) but the entity parameter is null - by doing a check against the ModelState.IsValid, it shows that the problem is a null ID (key) value. This is unsurprising because the database uses a Database Generated Identity for the ID column and therefore the ID would be created when the entity is saved into the database context.
I've therefore tried all sorts of ways of marking the ID column as database generated, but haven't managed to find anything. Strangely, I can't seem to find even one post of someone asking for this - surely I can't be the only one?!
I noted that when looking at the EF modelbuilder (for example here: http://forums.asp.net/t/1848984.aspx/1) there appears to be a means of affecting the model builder with a .HasDatabaseGeneratedOption property, but no similar option exists in the System.Web.Http.OData equivalent.
So the questions therefore are:
Is there a means of altering the model builder (or something else) so that the controller will accept the object and deserialize the entity even with a null key value?
If so, how can I do this?
If not, any suggestions as to other options?
I realise that I could potentially just populate the object with an (in this case) integer value from the client request, but this seems a) semantically wrong and b) won't necessarilly always be possible as a result of the client toolkit that might be used.
All help gratefully received!
Many thanks,
J.
You need to create a viewmodel for insert which does not contain the ID parameter. Use Automapper to map the properties of the incoming insert-model to your data entities.
The problem that you're having is that ID is a required attribute in your data model because it is your PK, except during insert, where it shouldn't be specified.
In my case, my database-generated key is a Guid.
As a work-around, in my TypeScript client code, I submit (via http POST) the object with an empty Guid like this: Note: ErrorId is the key column.
let elmahEntry: ELMAH_Error = {
Application: 'PTUnconvCost',
Host: this.serviceConfig.url,
Message: message,
User: that.userService.currentUserEmail,
AllXml: `<info><![CDATA[\r\n\r\n${JSON.stringify(info || {})}\r\n\r\n]]></info>`,
Sequence: 1,
Source: source,
StatusCode: 0,
TimeUtc: new Date(Date.now()),
Type: '',
ErrorId: '00000000-0000-0000-0000-000000000000'
};
Then, in my WebApi OData controller, I check to see if the key is the empty guid, and if so, I replace it with a new Guid, like this:
// POST: odata/ELMAH_Error
public IHttpActionResult Post(ELMAH_Error eLMAH_Error)
{
if (eLMAH_Error.ErrorId == Guid.Empty)
{
eLMAH_Error.ErrorId = Guid.NewGuid();
}
if (!ModelState.IsValid)
{
return BadRequest(ModelState);
}
db.ELMAH_Error.Add(eLMAH_Error);
try
{
db.SaveChanges();
}
catch (DbUpdateException)
{
if (ELMAH_ErrorExists(eLMAH_Error.ErrorId))
{
return Conflict();
}
else
{
throw;
}
}
return Created(eLMAH_Error);
}
I have the following Edit method:
[HttpPost]
public ActionResult Edit(Movie movie)
{
try
{
_db.ApplyCurrentValues("Movies1",movie);
_db.SaveChanges();
return RedirectToAction("Index");
}
catch
{
return View();
}
}
I get the error below when I run it:
An object with a key that matches the key of the supplied object could not be found in the ObjectStateManager. Verify that the key values of the supplied object match the key values of the object to which changes must be applied.
A couple points:
I did not get the error the first time I did an update, only subsequent updates.
Movies1 is the the name of the EntitySet when I view the edmx designer. Is this what it shold be or should it be the name of the table (Movie)?
I have seen things regarding Attach, but I am confused as to what exactly that is.
Inorder to apply current values an entity with that given key should be present in ObjectStateManager. The documentation for the ApplyCurrentValues states
Copies the scalar values from the supplied object into the object in
the ObjectContext that has the same key.
You can attach the entity and apply current values.
_db.Movies.Attach(movie);
_db.ObjectStateManager.ChangeState(movie, EntityState.Modified);
_db.SaveChanges();
A majority of the examples I see now are either using the Code First Approach or using an older version of MVC and the Entity Framework.
Assume I have a movie to update and I get to the Edit View, in the Edit method with the Post verb, what is the proper way to update a Movie? The first Edit Method below gets me to the Edit View with the populated Movie values and the second one is the one I want to use to update, I have tried some things, but nothing updates the data.
public ActionResult Edit(int id)
{
var movie = (from m in _db.Movies1
where m.Id == id
select m).First();
return View(movie);
}
[HttpPost]
public ActionResult Edit(Movie movie)
{
try
{
// TODO: Add update logic here
//What do I need to call to update the entity?
_db.SaveChanges();
return RedirectToAction("Index");
}
catch
{
return View();
}
}
Assuming that _db is derived from ObjectContext you have two options:
Change the state of the entity to Modified:
_db.Movies1.Attach(movie);
_db.ObjectStateManager.ChangeObjectState(movie, EntityState.Modified);
_db.SaveChanges();
This marks all properties of movie as modified and will send an UPDATE statement to the database which includes all column values, no matter if the values really changed or not.
Reload the original entity from the database and apply the changes to it:
var originalMovie = (from m in _db.Movies1
where m.Id == movie.Id
select m).First();
// You actually don't need to assign to a variable.
// Loading the entity into the context is sufficient.
_db.Movies1.ApplyCurrentValues(movie);
_db.SaveChanges();
ApplyCurrentValues will mark only those properties as modified which really did change compared to the original and the UPDATE statement which will be sent to the database only includes the changed column values. So, the UPDATE statement is potentially smaller than in the first example but you have to pay the price to reload the original entity from the database.
Edit
How does the second code example work?
When you run a query using the context (_db) Entity Framework does not only retrieve the entity from the database and assign it to the left side of the query (originalMovie) but it actually stores a second reference internally. You can think of this internal context "cache" as a dictionary of key-value pairs - the key is the entity primary key and the value is the entity itself, the same object as originalMovie refers to.
ApplyCurrentValues(movie) looks up this entity in the context's internal dictionary: It takes the key property value Id of the passed in movie, searches for an entity with that key in the internal dictionary and then copies property by property from the passed in ("detached") movie to the internal ("attached") entity with the same key. EF's change tracking mechanism marks the properties as Modified which were actually different to create later the appropriate UPDATE statement.
Because of this internal reference to the original entity you do not need to hold your own reference: That's the reason why originalEntity is not used in the code. You can in fact remove the assignment to the local variable altogether.
The example would not work if you disable change tracking when you load the original entity - for example by setting _db.Movies1.MergeOption = MergeOption.NoTracking;. The example relies on enabled change tracking (which is the default setting when entities are loaded from the database).
I cannot say which of the two examples has better performance. That might depend on details like size of the entities, number of properties which have been changed, etc.
It's worth to note though that both approaches do not work if related entities are involved (for example movie refers to a category entity) and if the relationship or the related entity itself could have been changed. Setting the state to Modified and using ApplyCurrentValues both affect only scalar and complex properties of movie but not navigation properties.
Your second edit method should look something like this:
[HttpPost]
public ActionResult Edit(int id, FormCollection collection)
{
var movie = (from m in _db.Movies1
where m.Id == id
select m).First();
if (TryUpdateModel(movie))
{
_db.SaveChanges();
return (RedirectToAction("Index"));
}
return View(movie);
}