This question relates to an MVC4 project with Entity Framework (database first)
I am passing an (EF) collection of 'Company' objects to a view.
I need to show the name of the 'Primary User' which is stored as int (foreign key) in each 'Company' object.
I am able to get the PrimaryUserID like this :
#foreach (var item in Model)
{
<div>#item.PrimaryUserID</div>
}
but I cannot figure out how to access the PrimaryUser object from the ID?
Is there a way to do this without passing a custom model containing the PrimaryUser object to my view?
Any help would be much appreciated!
//EDIT - this is how I currently pass the collection to my view
public ActionResult Installers(int id = 0)
{
CompanyType installer = db.CompanyTypes.Single(ct => ct.Description == "Installer");
return View(installer.Companies.ToList());
}
You can use the Navigation Property in your model.
Make sure your have included the property in your EF query.
( This is called "eager loading" )
public ActionResult Installers(int id = 0)
{
CompanyType installer =
db.CompanyTypes
.Include( ct => ct.Companies.Select( c => c.PrimaryUser ) )
.Single( ct => ct.Description == "Installer" );
return View( installer.Companies.ToList() );
}
Then just access the property in your markup:
<div>#item.PrimaryUser.Name</div>
Do you have a navigational property set up to (what is your presumably) your users table in your EDMX? Ordinarily you'd just be able to do something like <div>#item.PrimaryUser.Name</div> if that was set up.
Related
I'm trying to use a Kendo UI grid in MVC and remote data. I want to only grab and display data from the DbSet, onload, where one of the fields, "Status", equals '1'. I thought this should be able to be accomplished in the controller:
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Read([DataSourceRequest] DataSourceRequest request)
{
using (var db = new MyData(false))
{
var data = db.Training.Where(d => d.Status == '1').Select(d => new Training {
Id = d.Id,
Name = d.Name,
Status = d.Status
}).ToDataSourceResult(request);
return Json(data, JsonRequestBehavior.AllowGet);
}
}
The above code gives me the error that "The entity or complex type 'Training' cannot be constructed in a LINQ to Entities query". Any suggestions on how to rewrite the Linq statement so it'll work, or maybe a way to do it within the grid to suppress any that do not have a Status of '1'?
Your code is trying to project to a mapped entity which is not allowed. Additionally it's redundant to do that as you already have your entities. Remember that .Select() is for mapping one type to another but the .Where() method is already returning a list of your entities (Training).
Remove the .Select() and the query should work:
var data = db.Training.Where(d => d.Status == '1').ToDataSourceResult(request);
I have two sub-types of a super-type "Entity", namely "Household" and "Involved Body".
I've modeled them as shown below in my database and they were auto-generated to the EF Model (again shown below).
database
edmx model
Using the default scaffolding for MVC I am able to add a new Household without any problems. However, when I try to add a new Involved Body I hit an error when it tries to add the Entity Type.
There only relevant (as far as I can tell) difference between the two sub-types is that the EntityType for a Household is hard-coded as "Household" whereas the EntityType for an Involved Body can be any EntityType except "Household" - this is selected from a list by the user.
The Create Action on the HTTP POST for the Involved Body throws an error relating to the foreign key between tEntity and tEntityType with the tEntityType being null. Code as follows:
[HttpPost]
public ActionResult Create([Bind(Exclude = "entityID")]tEntity tentity
, tInvolvedBody tinvolvedbody
, tAddress taddress
, tAddressEntity taddressentity
//, tEntityType tentitytype
, int entityTypeID
)
{
#region entity type
//find entity type from id
var tentitytype = db.tEntityTypes.Find(entityTypeID);
#endregion
#region address
//assume start date of involved body not needed for reporting
taddressentity.startDate = DateTime.Now.Date;
#endregion
if (ModelState.IsValid)
{
db.tEntities.Add(tentity);
db.tInvolvedBodies.Add(tinvolvedbody);
db.tAddresses.Add(taddress);
db.tAddressEntities.Add(taddressentity);
db.SaveChanges();
return RedirectToAction("Index");
}
//recreate viewbag for entityType dropdown
var q = (
from e in db.tEntityTypes
where e.entityType != "Household"
select e
);
ViewBag.entityTypeID = new SelectList(q, "entityTypeID", "entityType");
return View(tinvolvedbody);
}
I've tried adding the tEntityType to the parameters list for the create but this results in the ModelState.IsValid returning false due to the entityType being null on all the objects.
I've also tried actively linking the entity type to each of the other objects using:
tentity.tEntityType = tentitytype;
tinvolvedbody.tEntity.tEntityType = tentitytype;
taddressentity.tEntity.tEntityType = tentitytype;
The above ends up working but it creates a new Entity for each of the other objects i.e. I get three new rows in my tEntity table, one is the Entity, one links to tInvolvedBody and one links to tAddressEntities. This makes no sense...
How can I insert a new InvolvedBody that creates an Entity, picks up the Entity Type and then links to the AddressEntity junction table?
Finally worked through this. Not sure if the answer is 'perfect' from a developer perspective but it works.
After intense debugging I realised that the navigation properties for the involved body and address entity were both looking for an entitytypeID which I had assumed would be provided by the entity object.
If I passed these in directly with the code shown:
tinvolvedbody.tEntity.tEntityType = tentitytype;
taddressentity.tEntity.tEntityType = tentitytype;
...I ended up with three new entitites and no relational data existing between all of {entity, involved body, address}
The code that works removes the explicit addition of a new entity and relies on EF to create an entity from the Involved Body. I then used the newly created entityID to map the address via addressentity as follows:
[HttpPost]
public ActionResult Create([Bind(Exclude="entityID")]tEntity tentity
,tInvolvedBody tinvolvedbody
,tAddress taddress
,tAddressEntity taddressentity
,int entityTypeID
)
{
#region entity type
var t =
(
from e in db.tEntityTypes
where (e.entityTypeID == entityTypeID)
select e
);
tinvolvedbody.tEntity.tEntityType = t.First();
#endregion
#region address
//assume start date of involved body not needed for reporting
taddressentity.startDate = DateTime.Now.Date;
#endregion
if (ModelState.IsValid)
{
db.tInvolvedBodies.Add(tinvolvedbody);
db.tAddresses.Add(taddress);
taddressentity.tEntity = db.tEntities.Find(tinvolvedbody.bodyID);
db.tAddressEntities.Add(taddressentity);
db.SaveChanges();
return RedirectToAction("Index");
}
Have you tried setting the typeID specifically? Also, from what I gathered from your model, the taddress is a child of taddressentity? As such, should it not be inserted first in order for the foreign key?
if (ModelState.IsValid)
{
tentity.entityTypeID = entityTypeID;
db.tEntities.Add(tentity);
tinvolvebody.bodyID= tentity.entityID
db.tInvolvedBodies.Add(tinvolvedbody);
taddressentity.entityID = tentity.entityID;
db.tAddressEntities.Add(taddressentity);
taddress.UPRN = taddressentity.UPRN;
db.tAddresses.Add(taddress);
db.SaveChanges();
return RedirectToAction("Index");
}
When I update my model I get an error on a child relation which I also try to update.
My model, say Order has a releationship with OrderItem. In my view I have the details of the order together with an editortemplate for the orderitems. When I update the data the link to Order is null but the orderid is filled, so it should be able to link it, TryUpdateModel returns true, the save however fails with:
InvalidOperationException: The operation failed: The relationship could not be changed because one or more of the foreign-key properties is non-nullable. When a change is made to a relationship, the related foreign-key property is set to a null value. If the foreign-key does not support null values, a new relationship must be defined, the foreign-key property must be assigned another non-null value, or the unrelated object must be deleted.]
My update method:
public ActionResult ChangeOrder(Order model)
{
var order = this.orderRepository.GetOrder(model.OrderId);
if (ModelState.IsValid)
{
var success = this.TryUpdateModel(order);
}
this.orderRepository.Save();
return this.View(order);
}
I tried all solutions I saw on SO and other sources, none succeeded.
I use .Net MVC 3, EF 4.3.1 together with DBContext.
There are a number of code smells here, which I'll try to be elegant with when correcting :)
I can only assume that "Order" is your EF entity? If so, I would highly recommend keeping it separate from the view by creating a view model for your form and copying the data in to it. Your view model should really only contain properties that your form will be using or manipulating.
I also presume orderRepository.GetOrder() is a data layer call that retrieves an order from a data store?
You are also declaring potentially unused variables. "var order =" will be loaded even if your model is invalid, and "var success =" is never used.
TryUpdateModel and UpdateModel aren't very robust for real-world programming. I'm not entirely convinced they should be there at all, if I'm honest. I generally use a more abstracted approach, such as the service / factory pattern. It's more work, but gives you a lot more control.
In your case, I would recommend the following pattern. There's minimal abstraction, but it still gives you more control than using TryUpdateModel / UpdateModel:
public ActionResult ChangeOrder(OrderViewModel model) {
if(ModelState.IsValid) {
// Retrieve original order
var order = orderRepository.GetOrder(model.OrderId);
// Update primitive properties
order.Property1 = model.Property1;
order.Property2 = model.Property2;
order.Property3 = model.Property3;
order.Property4 = model.Property4;
// Update collections manually
order.Collection1 = model.Collection1.Select(x => new Collection1Item {
Prop1 = x.Prop1,
Prop2 = x.Prop2
});
try {
// Save to repository
orderRepository.SaveOrder(order);
} catch (Exception ex) {
ModelState.AddModelError("", ex.Message);
return View(model);
}
return RedirectToAction("SuccessAction");
}
return View(model);
}
Not ideal, but it should serve you a bit better...
I refer you to this post, which is similar.
I assume that the user can perform the following actions in your view:
Modify order (header) data
Delete an existing order item
Modify order item data
Add a new order item
To do a correct update of the changed object graph (order + list of order items) you need to deal with all four cases. TryUpdateModel won't be able to perform a correct update of the object graph in the database.
I write the following code directly using a context. You can abstract the use of the context away into your repository. Make sure that you use the same context instance in every repository that is involved in the following code.
public ActionResult ChangeOrder(Order model)
{
if (ModelState.IsValid)
{
// load the order from DB INCLUDING the current order items in the DB
var orderInDB = context.Orders.Include(o => o.OrderItems)
.Single(o => o.OrderId == model.OrderId);
// (1) Update modified order header properties
context.Entry(orderInDB).CurrentValues.SetValues(model);
// (2) Delete the order items from the DB
// that have been removed in the view
foreach (var item in orderInDB.OrderItems.ToList())
{
if (!model.OrderItems.Any(oi => oi.OrderItemId == item.OrderItemId))
context.OrderItems.Remove(item);
// Omitting this call "Remove from context/DB" causes
// the exception you are having
}
foreach (var item in model.OrderItems)
{
var orderItem = orderInDB.OrderItems
.SingleOrDefault(oi => oi.OrderItemId == item.OrderItemId);
if (orderItem != null)
{
// (3) Existing order item: Update modified item properties
context.Entry(orderItem).CurrentValues.SetValues(item);
}
else
{
// (4) New order item: Add it
orderInDB.OrderItems.Add(item);
}
}
context.SaveChanges();
return RedirectToAction("Index"); // or some other view
}
return View(model);
}
Entity:
public class Page
{
//...
public virtual Page Parent { get; set; }
}
Need to set Parent field to null. Tried this, but no luck:
// Existing entity
Page pageAttached = db.Pages.First(x => x.Id == page.Id);
db.Entry(pageAttached).CurrentValues.SetValues(page);
if (model.ParentId != null)
pageAttached.Parent = db.Pages.First(x => x.Id == model.ParentId);
else
pageAttached.Parent = null; //does nothing
db.SaveChanges();
Parent is not a "complex field", it is a "Navigation Property".
Does it work if you do this?
// Existing entity
Page pageAttached = db.Pages.Include(x => x.Parent).First(x => x.Id == page.Id);
db.Entry(pageAttached).CurrentValues.SetValues(page);
if (model.ParentId != null)
pageAttached.Parent = db.Pages.First(x => x.Id == model.ParentId);
else
pageAttached.Parent = null; //does nothing
db.SaveChanges();
Response to comment 1
No, I meant .Include(x => x.Parent). I prefer strongly-typing using the lambda overload. Keeps magic strings out of the code.
The reason this works is because DbContext uses dynamically generated proxy classes for lazy loading. When you only query for .First(x => x.Id == page.Id), the object returned is really a class that implements your Page entity as its base class. (This is why collection and navigation properties have to be marked virtual, so they can be overridden in the dynamic proxies.) Furthermore, the dynamically generated proxy has a null Parent reference, even if there is a parent in the db.
It is not until the Parent property get method is invoked that EF hits the db to lazily load the parent. This is when it finds out whether the db actually has a null or non-null Parent property. So, when you set .Parent = null before the parent is actually lazily loaded, EF does nothing because it's already null.
The code I suggested uses .Include to eager load the Parent property. This means that the db gets both the child + its parent in a single db call. Now when you set null, the DbContext will track the change and remove the relationship during your next SaveChanges.
I've got a field which its type is byte[]. This field will hold my entity's RecordVersion property (timestamp in the database). How do I keep this field so that when I save my entity it is available?
I've tried two different things and haven't succeeded so far:
This renders "System.Byte[]":
<%= Html.Hidden("RecordVersion", Model.RecordVersion.ToString()) %>
This throws a ModelStateError where the type couldn't be converted:
ViewData["RecordVersion"] = entity.RecordVersion
Apparently the default MVC's mechanism that does the bind/unbind doesn't like much byte[] fields .....
You need to make a modelbinder and register it.
This article shows how to use a timestamp from a linq database in a hidden field much like what you are doing.
ModelBinders.Binders.Add(typeof(Binary), new LinqBinaryModelBinder());
In global.asax to register it.
That LinqBinaryModelBinder is in the futures assembly. If you want to user byte[] you'll have to write one yourself.
Have you tried.
<%= Html.Hidden("RecordVersion", System.Text.Encoding.Unicode.GetString(Model.RecordVersion)) %>
I wouldn't put the timestamp on the form. If you want to keep the object around I'd cache it server side and retrieve it from the cache using the id. Otherwise, you can re-retrieve the object from the database and apply the changes from your form data. The latter is what I do, using TryUpdateModel.
public ActionResult Update( int id )
{
using (var context = new DataContext())
{
var model = context.Models.Where( m => m.ID == id ).Single();
if (TryUpdateModel( model ))
{
...
context.SubmitChanges(); // wrapped in try/catch
...
}
else
{
...
}
}
return RedirectToAction( "Show", new { id = id } );
}