I have a single page which collects related data into a series of input fields.
When the user clicks submit I want to insert the data into two different database tables in one go. ie I want to get the primary key from the first insert, and then use it for the second insert operation.
I am hoping to do this all in one go, but I am not sure of the best way to do this with the Models/Entities in MVC.
Are you using LINQ or some other ORM? Typically these will support the ability to add a related entity and handle the foreign key relationships automatically. Typically, what I would do with LINQtoSQL is something like:
var modelA = new ModelA();
var modelB = new ModelB();
UpdateModel( modelA, new string[] { "aProp1", "aProp2", ... } );
UpdateModel( modelB, new string[] { "bProp1", "bProp2", ... } );
using (var context = new DBContext())
{
modelA.ModelB = modelB;
context.ModelA.InsertOnSubmit( modelA );
context.SubmitChanges();
}
This will automatically handle the insertion of modelA and modelB and make sure that the primary key for modelA is set properly in the foreign key for modelB.
If you are doing it by hand, you may have to do it in three steps inside a transaction, first inserting modelA, getting the key from that insert and updating modelB, then inserting modelB with a's data.
EDIT: I've shown this using UpdateModel but you could also do it with model binding with the parameters to the method. This can be a little tricky with multiple models, requiring you have have separate prefixes and use the bind attribute to specify which form parameters go with which model.
Related
I have a table UserStoreName,
Columns are :
int Id
string UserNameId (as a FK of the table AspNetUsers (Column Id))
sring StoreName
I have a page AddStore, a very simple page where user just enter the store name into the StoreName Field.
I already know the UserNameId, i'm taking it from the User.
So when user populate the storeName field and click submit i just need to add a record to the table UserStoreName.
sounds easy.
when i click submit the AddStore function from the controller is giving me ModelState.IsValid = false.
reason for that is cause userNameId is a required field.
i want to populate that field in the AddStore
function but when we get there the modelState is already invalid because of a required field in userStoreNameId enter code here
Here is the AddStore in case it will help :
[HttpPost]
[ValidateAntiForgeryToken]
public IActionResult AddStore(UserStoreName userStoreName)
{
userStoreName.UserNameId =
(_unitOfWork.ApplicationUser.GetAll().Where(q => q.UserName == User.Identity.Name).Select(q => q.Id)).FirstOrDefault();
userStoreName.UserName = User.Identity.Name;
userStoreName.IsAdminStore = false;
if (ModelState.IsValid)
{
_unitOfWork.UserStoreName.Add(userStoreName);
_unitOfWork.Save();
return RedirectToAction(nameof(Index));
}
return View(userStoreName);
}
Any idea what am i doing wrong? new to asp.net core mvc, its my first project.
Thanks :)
Thank you
If the UserNameId field is required, it must be supplied to pass model validation.
There are two ways around this. First, you could create a View Model, with just the fields you plan on actually submitting, and use it in place of the userStoreName variable. Then in the controller action, you can just instantiate a new UserStoreName object, and fill out the fields.
Alternatively, you could pass the UserNameId variable to the view, and populate the model client side using a hidden field, so it passes validation when returned to the controller. Hidden fields can potentially have their values edited client-side, however, so it may be worth checking the value again server side, especially if there are any security implications.
Foreign keys can be nullable so just make sure the UserNameId field is not marked with the "[Required]" Data Annotation in your model.
You'll also need to make sure that the column is nullable on the UserStoreName table to match the model otherwise it'll cause problems if your model is different from its underlying table.
Just a small suggestion also, I wouldn't foreign key on strings, I would change your model foreign key to an int, and make sure that the column in the table it's related to is also an int. It's a lot safer to do so, especially if you're dealing with IDENTITY columns.
If there is anything wrong with the reference, an exception will throw when the code tries to save your change, usually because the value it has in the FK reference cannot be found in the related table.
I've been trying to update an Entity using the following code:
var db = new MyContext();
var data = db.Tableau.Find(Id);
if (data != null)
{
data.Name = model.Name;
data.EmbedCode = model.EmbedCode;
db.SaveChanges();
}
The problem is that my Tableaus table has a Parent field (FK not null to a DataTree table). Sometimes when I save the changes to this edited record, I get an error saying that "The Parent field is required". But I am not editing the Parent field. The parent field should be intact and existent, since I am only altering the Name and EmbedCode fields.
How to proceed? Thanks in advance.
That is because you are allowing null values in ParentId column in your Tableaus table, but in your Tableau entity you have ParentId as non-nullable property( which it means the relationship is required), and when you load a Tableau instance from your DB, EF expects that you set that property too. Try changing that property to nullable:
public int? ParentId {get;set;}
If you configure your relationship using Fluent Api it would be:
modelBuilder.Entity<Tableau>()
.HasOptional(t=>t.Parent)
.WithMany(dt=>dt.Tablous)// if you don't have a collection nav. property in your DataTree entity, you can call this method without parameter
.HasForeignKey(t=>t.ParentId);
Update 1
If you want ParentId property as Required in your Tableau entity, you need to make sure that you have a valid value in that column in your DB per each row. With a "valid value" I mean it should be different of the default value and it should exist as PK in your DataTree table.
Update 2:
One way to load a related entity as part of your query is using Include extension method:
var data = db.Tableau.Include(t=>t.Parent).FirstOrDefault(t=>t.Id==Id);
Web services cannot return an anonymous type.
If you are building a LINQ query using classes through a datacontext... you cannot construct instances of those classes in a query.
Why would I want to do this? Say I want to join three "tables" or sets of objects. I have three items with a foreign key to each other. And say the lowest, most detailed of these was represented by a class that had fields from the other two to represent the data from those. In my LINQ query I would want to return a list of the lowest, most detailed class. This is one way I have decided to "join some tables together" and return data from each of them via LINQ to SQL via a WebService. This may be bad practice. I certainly do not like adding the additional properties to the lowest level class.
Consider something like this... (please ignore the naming conventions, they are driven by internal consideration) also for some reason I need to instantiate an anonymous type for the join... I don't know why that is... if I do not do it this way I get an error...
from su in _dataContext.GetTable<StateUpdate>()
join sfs in _dataContext.GetTable<SystemFacetState>()
on new { su.lngSystemFacetState } equals new { lngSystemFacetState = sfs.lngSystemFacetState }
join sf in _dataContext.GetTable<SystemFacet>()
on new { sfs.lngSystemFacet } equals new { lngSystemFacet = sf.lngSystemFacet }
join s in _dataContext.GetTable<System>()
on new { sf.lngSystem } equals new {lngSystem = s.lngSystem}
select new
{
lngStateUpdate = su.lngStateUpdate,
strSystemFacet = sf.strSystemFacet,
strSystemFacetState = sfs.strSystemFacetState,
dtmStateUpdate = su.dtmStateUpdate,
dtmEndTime = su.dtmEndTime,
lngDuration = su.lngDuration,
strSystem = s.strSystem
}
).ToList();
Notice I have to build the anonymous type which is composed of pieces of each type. Then I have to do something like this... (convert it to a known type for transport via the web service)
result = new List<StateUpdate>(from a in qr select(new StateUpdate
{
lngStateUpdate = a.lngStateUpdate,
strSystemFacet = a.strSystemFacet,
strSystemFacetState = a.strSystemFacetState,
dtmStateUpdate = a.dtmStateUpdate,
dtmEndTime = a.dtmEndTime,
lngDuration = a.lngDuration,
strSystem = a.strSystem
}));
It is just awful. And perhaps I have created an awful mess. If I am way way off track here please guide me to the light. I feel I am missing something fundamental here when I am adding all these "unmapped" properties to the StateUpdate class.
I hope someone can see what I am doing here so I can get a better way to do it.
You can create a 'dto' class which just contains the properties you need to return and populate it instead of the anonymous object:
public class Result
{
public string lngStateUpdate
{
get;
set;
}
... // other properties
}
then use it like this:
from su in _dataContext.GetTable<StateUpdate>()
...
select new Result
{
lngStateUpdate = su.lngStateUpdate,
... // other properties
}
Nitpick note - please ditch the Hungarian notation and camel casing for properties :)
I think the answer is to create another object to serve as a DTO. This object would not be mapped to the data context and can contain fields that cross the mapped objects. This solves the problems of repetitive properties in the mapped objects, and allows for instantiation of the DTO class in the query as it is not mapped.
FYI: with respect to the problem with the join- I revisited that and I think I may have had the inner and outer components of the join switched around before.
Using Breeze, what is the simplest way to populate a GUID key when an entity is created?
I'll assume that your entity is configured such that the client is responsible for setting the Guid key for new entities. That's the default for the Guid key of an Entity Framework Code First entity; it is as if the key property were adorned with [DatabaseGenerated(DatabaseGeneratedOption.None)]
The obvious approach is to set the key after creating the entity and before adding it to the manager, e.g.:
function createFoo() {
var foo = fooType.createEntity();
foo.id(breeze.core.getUuid()); // Knockout implementation
manager.addEntity(foo);
}
This may be all you ever need.
On the other hand, you may find that you're creating new Foos in many places and for some strange reason you can't use the createFoo function. You certainly don't want to repeat that code.
You can extend the Foo entity type with id-setting behavior after which you'd be able to write:
function createFoo() {
var foo = fooType.createEntity(); // foo.id is set for you
manager.addEntity(foo);
}
There are two approaches to consider - custom constructor and type initializer; both are described in "Extending Entities"
Constructor
You can initialize the key inside a custom constructor. Breeze calls the constructor both when you create the entity and when it materializes a queried entity. Breeze will replace the initial key value when materializing.
Here's an example that assumes the Knockout model library.
function Foo() {
foo.id(breeze.core.getUuid()); // using KO
}
// one way to get the MetadataStore
var store = manager.metadataStore;
// register the ctor with the Foo type
store.registerEntityTypeCtor("Foo", Foo);
Pretty simple. The only downside is that Breeze will generate a Guid every time it makes an entity, whether creating a new one or materializing one from a query. It's wasted effort during materialization but so what? Well, I suppose that might become a performance issue although I wouldn't assume so until I had measured it.
Initializer
Suppose you measured and the repeated Guid generation is a serious problem (really?). You could set the key in a type initializer instead and only call the Guid generator when creating a new entity.
Breeze calls a type initializer after the entity has been created or materialized from query just before returning that entity to the application. Clearly you don't want to overwrite a materialized key from the database so you'll test the key value to make sure it's not real (i.e. to make sure you're fixing a created entity) before assigning it. Here's an example.
function fooInitializer(foo) {
var emptyGuid = "00000000-0000-0000-0000-000000000000";
if (foo.id() !=== emptyGuid) {
foo.id(breeze.core.getUuid());
}
}
var store = manager.metadataStore;
// register the initializer; no ctor in this example
store.registerEntityTypeCtor("Foo", function(){}, fooInitializer);
Assuming you have a Guid surrogate Key on all your entities like we have in our case, you could code a createInstance factory that does the following in a very generic approach:
function createInstance(breezeEntityManager, typeName) {
var keyProperty = breezeEntityManager.metadataStore.getEntityType(typeName, false).dataProperties.filter(function (p) {
return p.isPartOfKey;
})[0];
var config = {};
config[keyProperty.name] = breeze.core.getUuid();
return breezeEntityManager.createEntity(typeName, config);
}
This way, you won't have to create an initializer for all your entities.
Im trying to get my head around attaching an entity with a related entity to a new context when I want to update the entity.
I have a Person Table (Generalised to Personnel), which has a LanguageID field. This field is linked as a FK via the EF to another table Language with LanguageID as the primary key (1-M). I need to update a particular Persons language preference, however, the relationship seems to remain linked to the old context as i get a "Object cannot be referenced by multiple instances of IEntityChangeTracker" error on the line marked below. Is there any way to attach the Language entity to the new context as a relationship of the Personnel (Person) entity???
The entities were not detached in the orginal GetPersonnel() method which uses an .Include() method to return the PreferredLanguage
PreferredLanguage is the NavigationProperty name on the Person table...
public static void UpdateUser(Personnel originalUser, Personnel newUser )
{
using (AdminModel TheModel = new AdminModel())
{
((IEntityWithChangeTracker)originalUser).SetChangeTracker(null);
((IEntityWithChangeTracker)originalUser.PreferredLanguage).SetChangeTracker(null);
TheModel.Attach(originalUser);--Error Line
TheModel.ApplyPropertyChanges("Person", newUser);
TheModel.SaveChanges();
}
}
Thanks
Sean
To avoid these sort of problems you should make GetPersonnel() do a NoTracking query.
I.e.
ctx.Person.MergeOption = MergeOption.NoTracking;
// and then query as per normal.
This way you can get a graph of connected entities (assuming you use .Include()) that is NOT attached. Note this won't work if you try to manually detach entities, because doing so schreds your graph.
Hope this helps
Alex