I am trying to learn about Breeze.js,
And it seems that Breeze requires that the back-end object has a PK defined.
I my case I am trying to read data from a SQL View.
Can Breeze query a SQL view using Breeze? What is the workaround or a better alternative for this.
Thanks,
Yes. My C# Model to SQL views looks exactly the same as those mappings to SQL tables.
Yes you can.
Breeze required PK for two way binding, that is send back modified object to server for save changes.
In your case it's only one way you can use SQL view.
The following is how i do it for a t-sql command. The same idea works for views (though we define those views in our model). Works great. Of course, no updating or adding, but that is to be expected.
internal class RvRDetail
{
public string DistrictName { get; set; }
public string EmployeeName { get; set; }
public string SiteName { get; set; }
public System.DateTime CalendarDate { get; set; }
public string RevenueCategoryName { get; set; }
public decimal TotalRepayment { get; set; }
public decimal TotalRevenue { get; set; }
}
[BreezeController]
public class SeasonlessRvRController : BreezeAbstractApiController
{
// GET: breeze/SeasonlessRvR/RvRData
[HttpGet]
public object RvRData(string districtList="", string showAllPeriods="0")
{
var returnData = _dbContextProvider.Context.Database
.SqlQuery<RvRDetail>("SELECT * from dbo.udf_SeasonlessRvR(#DistrictList, #ShowAllPeriods)",
new SqlParameter("#DistrictList", districtList),
new SqlParameter("#ShowAllPeriods", showAllPeriods))
.ToList();
return returnData;
}
}
Related
Useing Entity framework I want to include an only the first level of children objects and not the children of child
I have these two classes:
public class BusinessesTBL
{
public string ID { get; set; }
public string FirstName { get; set; }
public string lastName { get; set; }
public ICollection<OffersTBL> OffersTBLs { get; set; }
}
public class OffersTBL
{
public int ID { get; set; }
public string Name { get; set; }
public int CatId { get; set; }
public string BusinessesTBLID { get; set; }
public virtual BusinessesTBL BusinessesTBLs { get; set; }
}
when I try to bring all offers according to CatId field, I need to return the BusinessesTBLs also, but the method also return offers again per each BusinessesTBL obj , My code is :
public IQueryable<OffersTBL> GetOffersTBLsCat(int id)
{
db.OffersTBLs.Include(s => s.BusinessesTBLs);
}
You can see the wrong result on :
http://mycustom.azurewebsites.net/api/OffersApi/GetOffersTBLsCat/4
As you can see it return all offers under each Business object while business object under each offer, And I want only to return offers with its Business object without offer under Business obj.
Could anyone help please?
I now see that a big part of the original answer is nonsense.
Sure enough, the reason for the endless loop is relationship fixup. But you can't stop EF from doing that. Even when using AsNoTracking, EF performs relationship fixup in the objects that are materialized in one query. Thus, your query with Include will result in fully populated navigation properties OffersTBLs and BusinessesTBLs.
The message is simple: if you don't want these reference loops in your results, you have to project to a view model or DTO class, as in one of the other answers. An alternative, less attractive in my opinion, when serialization is in play, is to configure the serializer to ignore reference loops. Yet another less attractive alternative is to get the objects separately with AsNoTracking and selectively populate navigation properties yourself.
Original answer:
This happens because Entity Framework performs relationship fixup, which is the process that auto-populates navigation properties when the objects that belong there are present in the context. So with a circular references you could drill down navigation properties endlessly even when lazy loading is disabled. The Json serializer does exactly that (but apparently it's instructed to deal with circular references, so it isn't trapped in an endless loop).
The trick is to prevent relationship fixup from ever happing. Relationship fixup relies on the context's ChangeTracker, which caches objects to track their changes and associations. But if there's nothing to be tracked, there's nothing to fixup. You can stop tracking by calling AsNoTracking():
db.OffersTBLs.Include(s => s.BusinessesTBLs)
.AsNoTracking()
If besides that you also disable lazy loading on the context (by setting contextConfiguration.LazyLoadingEnabled = false) you will see that only OffersTBL.BusinessesTBLs are populated in the Json string and that BusinessesTBL.OffersTBLs are empty arrays.
A bonus is that AsNoTracking() increases performance, because the change tracker isn't busy tracking all objects EF materializes. In fact, you should always use it in a disconnected setting.
You have deactivated lazy loading on OffersTBLs making it non-virtual. What if you activate lazy loading? like this:
public class BusinessesTBL
{
public string ID { get; set; }
public string FirstName { get; set; }
public string lastName { get; set; }
//put a virtual here
public virtual ICollection<OffersTBL> OffersTBLs { get; set; }
}
Then, be sure to not call/include OffersTBLs when serializing. If the OffersTBLs are still returning, it is because you are fetching them somewhere in your code. If this is happening, edit your question and paste all the code, including the serializing logic.
Since OffersTBL has an association to BusinessesTBL and BusinessesTBL to OffersTBL you can loop infinitly throw the Entities like OffersTBL.BusinessesTBL.OffersTBL.BusinessesTBL and so on.
To control the nested depth of the Entities i'm usually using helperclasses with the needed properties in them.
For BusinessesTBL
public class BusinessesTBLHelper
{
private BusinessesTBLHelper(BusinessesTBL o){
ID = o.ID;
FirstName = o.FirstName;
lastName = o.LastName;
OffersTBLids = new List<int>();
foreach(OffersTBL offersTbl in o.OffersTBLs){
OffersTBLids.Add(offersTbl.ID);
}
}
public string ID { get; set; }
public string FirstName { get; set; }
public string lastName { get; set; }
public IEnumerable<int> OffersTBLids { get; set; } //no references anymore
}
And same for your OffersTBL Entity.
public class OffersTBLHelper
{
private OffersTBLHelper(OffersTBL o){
ID = o.ID;
Name = o.Name;
CatId = o.CatId;
BusinessesTBLID = o.BusinessesTBLID;
BusinessesTBLs = new BusinessesTBLHelper(o.BusinessesTBLs);
}
public string ID { get; set; }
public string Name{ get; set; }
public intCatId{ get; set; }
public string BusinessesTBLID { get; set; }
public BusinessesTBLHelper BusinessesTBLs { get; set; }
}
On quering database you can directly create the new helperobjects from queryresult:
public IEnumerable<OffersTBLHelper> GetOffersTBLsCat(int id)
{
return db.OffersTBLs.where(s => s.CatId == id).Select(x=> new OffersTBLHelper(x)).ToList();
}
Now you have all the OffersTBL with BusinessesTBLs under. The loop stops here because the BusinessesTBLs have no OffersTBL under it. However, it only has them Ids in a List for further referencing and identifying.
Assuming that the object isnt null and just empty:
public IQueryable<OffersTBL> GetOffersTBLsCat(int id)
{
db.OffersTBLs.Include(s => s.BusinessesTBLs).Where(x => !x.BusinessesTBLs.OffersTBLs.Any());
}
Edit: Filter before the include:
public IQueryable<OffersTBL> GetOffersTBLsCat(int id)
{
db.OffersTBLs.Where(x => !x.BusinessesTBLs.OffersTBLs.Any())
.Include(s => s.BusinessesTBLs);
}
How can I use Entity Framework and Migration to add a CreationDate and ModifiedDate to some (not all) of my Model-classes to automatically update the Database, and also automatically update the Database for these fields with the current DateTime?
To make it more clear, this is what I'd like to add using Migration to two of my Database-tables:
CreationDate DATETIME DEFAULT NULL,
ModifiedDate TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
I've added them in the Model like this:
public DateTime? CreationDate { get; set; }
public int ModifiedDate { get; set; }
My only idea I had so far is: Override the DbContext#SaveChanges() to something like:
public void SaveChanged()
{
// Somehow check if the Tables in the Data I want to update contains a ModifiedDate
// or Data I want to create contains a CreationDate
// And add them with the current DateTime if these fields are present in the table(s)
base.SaveChanges();
}
I don't even know if this above is possible and how I can access the LINQ-query I want to use on the Database, but if this is the right direction, what should I put at the comment-lines? And if this isn't the correct way of handling this, how should I do this then?
TL;DR: How to use Entity Framework Migration on a Model(-Field) so it uses ON UPDATE CURRENT_TIMESTAMP?
If you enable automatic migrations, the model will be updated when your application instances the DbContext for the first time in your application. That usually happens the first time the application uses the DbContext for some CRUD operatiosn, but it can also be triggered by calling the DbContext.Database.Initialize method. But you don't need to do it!!
To understand how to enable automatic migrations, and how they work, read thoroughfully this document: Automatic Code First Migrations on MSDN. You can easyly navigate from this docuemnt to other related ones to improve your understanding of EF.
The attributes in your class are correct, but you don't need to specify those related to the DateTime property: EF conventions will make a DateTime property the desired type on the DB side (a nullable DATETIME in this case).
NOTE: a timestamp has nothing to do with a date, it's an incrementing number to mark the "version" of the row, i.e. it changes whenever the row is updated, but it's not a date but a number
I know this is old but the only answer doesn't even come close to answering the right question!
Here's how to do it:
Just loop the ChangeTracker collection in the DbContext like this:
public virtual int SaveChanges()
{
foreach (var item in this.ChangeTracker.Entries())
{
var now = DateTime.UtcNow;
var modelBase = item.Entity as IModelBase;
if (modelBase != null)
{
switch (item.State)
{
case EntityState.Added:
modelBase.CreatedOn = now;
goto case EntityState.Modified;
case EntityState.Modified:
modelBase.LastModifiedOn = now;
break;
default:
break;
}
}
}
return base.SaveChanges();
}
You also need an interface and preferably a base class like below:
/// <summary>New interface classes should implement if they already have a base class.</summary>
///
public interface IModelBase
{
[Key]
string Id { get; set; }
DateTime CreatedOn { get; set; }
DateTime LastModifiedOn { get; set; }
string CreatedById { get; set; }
string LastModifiedById { get; set; }
}
/// <summary>Base class model classes should inherit if they do not have an existing base class. Any MVC framework classes with existing base classes should implement the interface instead.</summary>
///
public class ModelBase:IModelBase
{
[Key]
public string Id { get; set; }
public DateTime CreatedOn { get; set; }
public DateTime LastModifiedOn { get; set; }
public string CreatedById { get; set; }
public string LastModifiedById { get; set; }
}
Then finally your model classes either need to inherit the base class or implement the interface:
public class MyTrackedClass : ModelBase
{
// Your code here!
}
Or
public class MyTrackedClass : IModelBase
{
[Key]
public string Id { get; set; }
public DateTime CreatedOn { get; set; }
public DateTime LastModifiedOn { get; set; }
public string CreatedById { get; set; }
public string LastModifiedById { get; set; }
// Your code here!
}
I have a DbDataController which delivers a List of Equipment.
public IQueryable<BettrFit.Models.Equipment> GetEquipment() {
var q= DbContext.EquipmentSet.OrderBy(e => e.Name);
return q;
}
In my scaffolded view everything looks ok.
But the Equipment contains a HashSet member of EquipmentType. I want to show this type in my view and also be able to add data to the EquipmentType collection of Equipment (via a multiselect list).
But if I try to include the "EquipmentType" in my linq query it fails during serialisation.
public IQueryable<BettrFit.Models.Equipment> GetEquipment() {
var q= DbContext.EquipmentSet.Include("EquipmentType").OrderBy(e => e.Name);
return q;
}
"Object Graph for Type EquipmentType Contains Cycles and Cannot be Serialized if Reference Tracking is Disabled"
How can I switch on the "backtracking of references"?
Maybe the problem is that the EquipmentType is back-linking through a HashSet? But I do not .include("EquipmentType.Equipment") in my query. So that should be ok.
How is Upshot generating the model? I only find the EquipmentViewModel.js file but this does not contain any model members.
Here are my model classes:
public class Equipment
{
public Equipment()
{
this.Exercise = new HashSet<Exercise>();
this.EquipmentType = new HashSet<EquipmentType>();
this.UserDetails = new HashSet<UserDetails>();
}
public int ID { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public string Picture { get; set; }
public string Link { get; set; }
public string Producer { get; set; }
public string Video { get; set; }
public virtual ICollection<EquipmentType> EquipmentType { get; set; }
public virtual ICollection<UserDetails> UserDetails { get; set; }
}
public class EquipmentType
{
public EquipmentType()
{
this.Equipment = new HashSet<Equipment>();
this.UserDetails = new HashSet<UserDetails>();
}
public int ID { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public virtual ICollection<Equipment> Equipment { get; set; }
public virtual ICollection<UserDetails> UserDetails { get; set; }
}
try decorating one of the navigation properties with [IgnoreDataMember]
[IgnoreDataMember]
public virtual ICollection<Equipment> Equipment { get; set; }
The model generated by upshot can be found on the page itself. In your Index view you will see the UpshotContext HTML helper being used (given that you are using the latest SPA version), in which the dataSource and model type are specified.
When the page is then rendered in the browser, this helper code is replaced with the actual model definition. To see that, view the source code of your page in the browser and search for a <script> tag that starts with upshot.dataSources = upshot.dataSources || {};
Check here for more info about how upshot generates the client side model.
As for the "backtracking of references", I don't know :)
I figured out - partially how to solve the circular reference problem.
I just iterated over my queried collection (with Include() ) and set the backreferences to the parent to NULL. That worked for the serialisation issue which otherwise already breaks on the server.
The only problem now is the update of a data entity - its failing because the arrays of the referenced entitycollection are static...
To solve the cyclic backreference, you can use the IgnoreDataMember attribute. Or you can set the back reference to NULL before returning the data from the DbDataController
I posted a working solution to your problem in a different question, but using Entity Framework Code First.
https://stackoverflow.com/a/10010695/1226140
Here I show how to generate your client-side model manually, allowing to you to map the data however you please
I have a class, which has 8 properties / 8 columns in DB. In the Edit page, I want to exclude the AddedDate and UserID fields. When a user edits a voucher, he can't overwrite the AddedDate or UserID values in the DB.
public class Voucher
{
public int ID { get; set; }
public string Title { get; set; }
public string SiteName { get; set; }
public string DealURL { get; set; }
public DateTime AddedDate { get; set; }
public DateTime? ExpirationDate { get; set; }
public string VoucherFileURL { get; set; }
public Guid UserID { get; set; }
}
Here is what I have for Edit controller:
// POST: /Voucher/Edit/5
[HttpPost]
public ActionResult Edit([Bind(Exclude = "AddedDate")]Voucher voucher)
{
if (ModelState.IsValid)
{
db.Entry(voucher).State = EntityState.Modified;
db.SaveChanges();
return RedirectToAction("Index");
}
return View(voucher);
}
On Edit page, when I click on submit, I got the following error:
System.Data.SqlServerCe.SqlCeException: An overflow occurred while converting to datetime.
Seems like the AddedDate didn't get excluded from the voucher object and triggered the error.
Would you please let me know how to fix it? Thanks!
(it is an updated version of asp.net mvc3 UpdateModel exclude properties is not working, I will go with another approach)
Never use your domain entities as action arguments and never pass your domain entities to your views. I would recommend you to use view models. In the view model you will include only the properties that you want to be bound from the view. The view model is a class that's specifically tailored to the requirements of a given view.
public class VoucherViewModel
{
public int ID { get; set; }
public string Title { get; set; }
public string SiteName { get; set; }
public string DealURL { get; set; }
public DateTime? ExpirationDate { get; set; }
public string VoucherFileURL { get; set; }
}
and then:
[HttpPost]
public ActionResult Edit(VoucherViewModel model)
{
// TODO: if the view model is valid map it to a model
// and pass the model to your DAL
// To ease the mapping between your models and view models
// you could use a tool such as AutoMapper: http://automapper.org/
...
}
UPDATE:
In the comments section #Rick.Anderson-at-Microsoft.com points out that while I have answered your question I haven't explained where the problem comes from.
The thing is that DateTime is a value type meaning it will always have a value. The [Bind(Exclude = "AddedDate")] works perfectly fine and it does what it is supposed to do => it doesn't bind the AddedDate property from the request. As a consequence the property will have its default value which for a DateTime field is 1/1/0001 12:00:00 AM and when he attempts to save this in SQL Server it blows because SQL Server doesn't support such format.
I have an object like this
public class ParentEntityInfo
{
public long? ParentId { get; set; }
public string EntityName { get; set; }
public string ParentProperty { get; set; }
}
and view for this object is:
<%=Html.Hidden("parentInfo.ParentId", parentInfo.ParentId)%>
<%=Html.Hidden("parentInfo.ParentProperty", parentInfo.ParentProperty)%>
<%=Html.Hidden("parentInfo.EntityName", parentInfo.EntityName)%>
I have the case where parentInfo is null and I post this form to controller. On the controller action
public ActionResult SomeAction(..., ParentEntityInfo parentInfo)
I receive constructed object parentInfo but all properties are null. In this case I would rather prefer to have whole parentInfo to be null. I there any possibility to tell default model binder do not pass such object? Or probably I can modify something in this code to make it work this way. I think in mvc 2.0 it worked this way.
Use the HiddenFor(...) helper instead.
I think the default model binder will always use Activator.CreateInstance to bind complex action parameters. What you can do is use ModelState.IsValid to assess whether the parameter was bound successfully. I think in your case this will be false by default, but if not you could add the necessary attribute to ensure this behaviour e.g.
public class ParentEntityInfo
{
[Required(ErrorMessage = "Parent required")]
public long? ParentId { get; set; }
public string EntityName { get; set; }
public string ParentProperty { get; set; }
}