I am starting to use breezejs for a project with a Web API 2.1 backend. I have an entity called Country that has a foreign key/navigation property to an entity called Continent.
I want to use the countries as lookup values but I also need their relationship to continents so I would like to fetch that info as well.
public class Country
{
public string Iso { get; set; }
public string Name { get; set; }
public virtual Continent Continent { get; set; }
}
I also have a FK field called continentIso but I don't use it in code.
Currently the backend controller looks like:
[HttpGet]
public object Lookups() {
var countries = _breezeRepository.Get<Country>().Include(it=>it.continent);
//more lookups in here
return new { countries };
}
As per the breeze samples I am returning an anonymous object of entities (I have a couple more but removed them from the above to avoid confusion).
On the front end side I have a lookup repository (demonstrated by John Papa's Building Apps with Angular and Breeze - Part 2):
function setLookups() {
this.lookupCachedData = {
countries: this._getAllLocal(entityNames.country, 'name'),
};
}
Problem is that although the sent JSON contains values for the continents, the countries object does not contain a value or a navigation property for them.
I have also tried bringing the continents as a separate lookup and try joining them through breeze metadata extension as I do for connecting lookups with entities but to no avail.
I also have a FK field called continentIso but I don't use it in code.
Probably that's the problem as explained here.
I would try the followings:
Make sure you have the Continent FK explicitly defined in your domain model. Eg.:
public class Country
{
public string Iso { get; set; }
public string Name { get; set; }
public string ContinentIso { get; set; }
public virtual Continent Continent { get; set; }
}
Also, in your controller, return not only the list of countries, but also the list of continents; breeze would make the binding. (not sure that the Include your have there is necessary).
[HttpGet]
public object Lookups() {
var countries = _breezeRepository.Get<Country>();
var countinents = _breezeRepository.Get<Continent>();
//more lookups in here
return new { countries, continents };
}
Related
I have a website that is using EF Core 3.1 to access its data. The primary table it uses is [Story] Each user can store some metadata about each story [StoryUserMapping]. What I would like to do is when I read in a Story object, for EF to automatically load in the metadata (if it exists) for that story.
Classes:
public class Story
{
[Key]
public int StoryId { get; set; }
public long Words { get; set; }
...
}
public class StoryUserMapping
{
public string UserId { get; set; }
public int StoryId { get; set; }
public bool ToRead { get; set; }
public bool Read { get; set; }
public bool WontRead { get; set; }
public bool NotInterested { get; set; }
public byte Rating { get; set; }
}
public class User
{
[Key]
public string UserId { get; set; }
...
}
StoryUserMapping has composite key ([UserId], [StoryId]).
What I would like to see is:
public class Story
{
[Key]
public int StoryId { get; set; }
public bool ToRead { get; set; } //From user mapping table for currently logged in user
public bool Read { get; set; } //From user mapping table for currently logged in user
public bool WontRead { get; set; } //From user mapping table for currently logged in user
public bool NotInterested { get; set; } //From user mapping table for currently logged in user
public byte Rating { get; set; } //From user mapping table for currently logged in user
...
}
Is there a way to do this in EF Core? My current system is to load the StoryUserMapping object as a property of the Story object, then have Non-Mapped property accessors on the Story object that read into the StoryUserMapping object if it exists. This generally feels like something EF probably handles more elegantly.
Use Cases
Setup: I have 1 million stories, 1000 users, Worst-case scenario I have a StoryUserMapping for each: 1 billion records.
Use case 1: I want to see all of the stories that I (logged in user) have marked as "to read" with more than 100,000 words
Use case 2: I want to see all stories where I have NOT marked them NotInterested or WontRead
I am not concerned with querying multiple StoryUserMappings per story, e.g. I will not be asking the question: What stories have been marked as read by more than n users. I would rather not restrict against this if that changes in future, but if I need to that would be fine.
Create yourself an aggregate view model object that you can use to display the data in your view, similar to what you've ended up with under the Story entity at the moment:
public class UserStoryViewModel
{
public int StoryId { get; set; }
public bool ToRead { get; set; }
public bool Read { get; set; }
public bool WontRead { get; set; }
public bool NotInterested { get; set; }
public byte Rating { get; set; }
...
}
This view model is concerned only about aggregating the data to display in the view. This way, you don't need to skew your existing entities to fit how you would display the data elsewhere.
Your database entity models should be as close to "dumb" objects as possible (apart from navigation properties) - they look very sensible as they are the moment.
In this case, remove the unnecessary [NotMapped] properties from your existing Story that you'd added previously.
In your controller/service, you can then query your data as per your use cases you mentioned. Once you've got the results of the query, you can then map your result(s) to your aggregate view model to use in the view.
Here's an example for the use case of getting all Storys for the current user:
public class UserStoryService
{
private readonly YourDbContext _dbContext;
public UserStoryService(YourDbContext dbContext)
{
_dbContext = dbContext;
}
public Task<IEnumerable<UserStoryViewModel>> GetAllForUser(string currentUserId)
{
// at this point you're not executing any queries, you're just creating a query to execute later
var allUserStoriesForUser = _dbContext.StoryUserMappings
.Where(mapping => mapping.UserId == currentUserId)
.Select(mapping => new
{
story = _dbContext.Stories.Single(story => story.StoryId == mapping.StoryId),
mapping
})
.Select(x => new UserStoryViewModel
{
// use the projected properties from previous to map to your UserStoryViewModel aggregate
...
});
// calling .ToList()/.ToListAsync() will then execute the query and return the results
return allUserStoriesForUser.ToListAsync();
}
}
You can then create a similar method to get only the current user's Storys that aren't marked NotInterested or WontRead.
It's virtually the same as before, but with the filter in the Where to ensure you don't retrieve the ones that are NotInterested or WontRead:
public Task<IEnumerable<UserStoryViewModel>> GetForUserThatMightRead(string currentUserId)
{
var storiesUserMightRead = _dbContext.StoryUserMappings
.Where(mapping => mapping.UserId == currentUserId && !mapping.NotInterested && !mapping.WontRead)
.Select(mapping => new
{
story = _dbContext.Stories.Single(story => story.StoryId == mapping.StoryId),
mapping
})
.Select(x => new UserStoryViewModel
{
// use the projected properties from previous to map to your UserStoryViewModel aggregate
...
});
return storiesUserMightRead.ToListAsync();
}
Then all you will need to do is to update your View's #model to use your new aggregate UserStoryViewModel instead of your entity.
It's always good practice to keep a good level of separation between what is "domain" or database code/entities from what will be used in your view.
I would recommend on having a good read up on this and keep practicing so you can get into the right habits and thinking as you go forward.
NOTE:
Whilst the above suggestions should work absolutely fine (I haven't tested locally, so you may need to improvise/fix, but you get the general gist) - I would also recommend a couple of other things to supplement the approach above.
I would look at introducing a navigation property on the UserStoryMapping entity (unless you already have this in; can't tell from your question's code). This will eliminate the step from above where we're .Selecting into an anonymous object and adding to the query to get the Storys from the database, by the mapping's StoryId. You'd be able to reference the stories belonging to the mapping simply by it being a child navigation property.
Then, you should also be able to look into some kind of mapping library, rather than mapping each individual property yourself for every call. Something like AutoMapper will do the trick (I'm sure other mappers are available). You could set up the mappings to do all the heavy lifting between your database entities and view models. There's a nifty .ProjectTo<T>() which will project your queried results to the desired type using those mappings you've specified.
i have this class which contains a list of the object ConversieDetail
public class ConversieRun
{
[Key]
public String Guid { get; set; }
public String Naam { get; set; }
public String Status { get; set; }
public DateTime Start { get; set; }
public DateTime? Einde { get; set; }
public List<ConversieDetails> Details { get; set; }
}
With the following method i need to return a list of ConversieRun including the ConversieDetails
public List<PGData.ConversieRun> GetAll()
{
//var result = _context.CoversieDetails.ToList();
return _context.ConversieRun.ToList();
}
however when i return with above example the conversieDetail List is null.
now when i uncomment the result list, the List of conversieDetails will be filled in the ConversieRun object as expected.
any reason why the list of ConversieDetails is null if i don't get them first in another list?
thanks in advance.
Relationships in entities are not loaded by default and will be null. You can explicitly tell EF to also load the related entities by using the Include like this:
_context.ConversieRun.Include(x => x.Details).ToList();
Now all ConversieRun entities will be loaded including their details.
You can read more about this in the "Loading Related Data" section of the documentation (https://learn.microsoft.com/en-us/ef/core/querying/related-data)
The example here is using the Explicit loading method, you can also choose to use the Lazy loading method where the related entities are loaded when you request them. This can however have a negative impact on the number of database queries as it would run a separate query for every ConversieRun entity to get its details.
Using fluent api, how do I map multiple properties of the same data type to a single table conditionally.
Database Model:
ListType would include the Grouping names i.e. Allergens
ListItem would include all possible values for the given type
ProductListItem contains all "selected" values for a given product.
The goal is to use the ProductListItem table and apply it across multiple properties of a model (of the same ProductListItem type) based on the ListType (WHERE ProductListItem.ListTypeID = 1).
public class Product
{
public int ProductID { get; set; }
public List<ProductListItem> Allergens { get; set; }
public List<ProductListItem> DoesNotContain { get; set; }
}
I really don't think that you can achieve this with conditional mapping, but you can cheat.
public List<ProductListItem> Allergens
{
get { return this.ProductListItems.Where(i => i.ListType.Name=="Allergens").ToList=();}
}
Or can you can optionally create a single class for different ListItems with the same baseclass and use the TPH mapping: http://weblogs.asp.net/manavi/inheritance-mapping-strategies-with-entity-framework-code-first-ctp5-part-1-table-per-hierarchy-tph
The code would be something like this:
class Product
{
public List<AllergenProductListItem> Allergens { get; set; }
public List<DoesNotContainListItem> DoesNotContain { get; set; }
}
Its obviously not dynamic regarding the number of the item types (hard to add a new one), but neither is you desired solution, since if you want to have a new type you should modify the code.
What are good strategies for rebuilding/enriching a nested or complex ViewModel?
A common way to rebuild a flat ViewModel is shown here
But building and rebuilding a nested ViewModel using that method is too complex.
Models
public class PersonInfo
{
public int Id { get; set; }
public string Name { get; set; }
public int Nationality { get; set; }
public List<Address> Addresses { get; set; }
}
public class Address
{
public int AddressTypeID { get; set; }
public string Country { get; set; }
public string PostalCode { get; set; }
}
public class AddressType
{
public int Id { get; set; }
public string Description { get; set; }
}
view models
public class PersonEditModel
{
public int Id { get; set; }
public string Name { get; set; } //read-only
public int Nationality { get; set; }
public List<AddressEditModel> Addresses { get; set; }
public List<SelectListItem> NationalitySelectList { get; set; } //read-only
}
public class AddressEditModel
{
public int AddressTypeId { get; set; }
public string AddressDescription { get; set; } //read-only
public string Country { get; set; }
public string PostalCode { get; set; }
public List<SelectListItem> CountrySelectList { get; set; } //read-only
}
actions
public ActionResult Update(int id)
{
var addressTypes = service.GetAddressTypes();
var person = service.GetPerson(id);
var personEditModel= Map<PersonEditModel>.From(person);
foreach(var addressType in addressTypes)
{
var address = person.Addresses.SingleOrDefault(i => i.AddressTypeId == addressType.Id)
if(address == null)
{
personEditModel.Addresses.Add(new AddressEditModel
{
AddressTypeId = addressType.Id
});
}
else
{
personEditModel.Addresses.Add(Map<AddressEditModel>.From(address));
}
}
EnrichViewModel(personEditModel, person, addressTypes); //populate read-only data such as SelectList
return Index(personEditModel);
}
[HttpPost]
public ActionResult Update(PersonEditModel editModel)
{
if(!ModelState.IsValid)
{
var person = service.GetPerson(editModel.Id);
var addressTypes = service.GetAddressTypes();
EnrichViewModel(editModel, person, addressTypes);
return View(editModel);
}
service.Save(...);
return RedirectToAction("Index");
}
//populate read-only data such as SelectList
private void EnrichViewModel(PersonEditModel personEditModel, Person person, IEnumerable<AddressType> addressTypes)
{
personEditModel.Name = person.Name;
personEditModel.NationalitySelectList = GetNationalitySelectList();
foreach(var addressEditModel in personEditModel.Addresses)
{
addressEditModel.Description = addressTypes.Where(i => i.Id = addressEditModel.AddressTypeId).Select(i => i.Description).FirstOrDefault();
addressEditModel.CountrySelectListItems = GetCountrySelectList(addressEditModel.AddressTypeId);
}
}
My code for building and rebuilding the ViewModels (PersonEditModel and AddressEditModel) is too ugly. How do I restructure my code to clean this mess?
One easy way is to always build a new view model instead of merging/rebuilding since MVC will overwrite the fields with the values in ModelState anyway
[HttpPost]
public ActionResult Update(PersonEditModel editModel)
{
if(!ModelState.IsValid)
{
var newEditModel = BuildPersonEditModel(editModel.Id);
return View(newEditModel);
}
but I'm not sure that this is a good idea. Is it? Are there other solutions besides AJAX?
I'm going to tackle your specific pain points one-by-one and I'll try to present my own experience and likely solutions along the way. I'm afraid there is no best answer here. You just have to pick the lesser of the evils.
Rebuilding Dropdownlists
They are a bitch! There is no escaping rebuilding them when you re-render the page. While HTML Forms are good at remembering the selected index (and they will happily restore it for you), you have to rebuild them. If you don't want to rebuild them, switch to Ajax.
Rebuilding Rest of View Model (even nested)
HTML forms are good at rebuilding the whole model for you, as long as you stick to inputs and hidden fields and other form elements (selects, textarea, etc).
There is no avoiding posting back the data if you don't want to rebuild them, but in this case you need to ask yourself - which one is more efficient - posting back few extra bytes or making another query to fetch the missing pieces?
If you don't want to post back the readonly fields, but still want the model binder to work, you can exclude the properties via [Bind(Exclude="Name,SomeOtherProperty")] on the view model class. In this case, you probably need to set them again before sending them back to browser.
// excluding specific props. note that you can also "Include" instead of "Exclude".
[Bind(Exclude="Name,NationalitySelectList")]
public class PersonEditModel
{
...
If you exclude those properties, you don't have to resort to hidden fields and posting them back - as the model binder will simply ignore them and you still will get the values you need populated back.
Personally, I use Edit Models which contain just post-able data instead of Bind magic. Apart from avoiding magic string like you need with Bind, they give me the benefits of strong typing and a clearer intent. I use my own mapper classes to do the mapping but you can use something like Automapper to manage the mapping for you as well.
Another idea may be to cache the initial ViewModel in Session till a successful POST is made. That way, you do not have to rebuild it from grounds up. You just merge the initial one with the submitted one in case of validation errors.
I fight these same battles every time I work with Forms and finally, I've started to just suck it up and go fully AJAX for anything that's not a simple name-value collection type form. Besides being headache free, it also leads to better UX.
P.S. The link you posted is essentially doing the same thing that you're doing - just that its using a mapper framework to map properties between domain and view model.
I am new to asp.net C# and trying to learn by building a simple web app based on MVC 3 Music application. So far i have had a decent run but i am running into this this and i am not able to figure out the root cause. plz help
I am building a simple website where Projects are listed, then clicking on projects you see all the tables and then clicking on table you see all the columns. Projects/Tables/Column are being fetched from SQL db which has valid data and PK/FK keys defined. i am able to navigate from projects to tables and can see all columns under tables but when I click on column link, i get error as described below.
ERROR: "Invalid column name 'Tables_Id'." SQL profiler shows this column in the query but i do not understand where is it coming from as I do not have any such columm.
CONTROLLER CLASS
public class ProjectController : Controller // Inherit from base class Controller
{
DbEntities storeDB = new DbEntities(); //Create Object/instance of class //StorDB is reference to an object
public ActionResult Index()
{
var Name = storeDB.ProjectNM.ToList(); //Use 'var' coz we may have any type returned, 'var' is determined at run time
return View(Name);
}
public ActionResult BrowseTables(string Projects)
{
var ProjectModel = storeDB.ProjectNM.Include ("Tabless")
.Single(g => g.Name == Projects);
return View(ProjectModel);
}
public ActionResult BrowseColumns(string TableIs)
{
var ProjectModel1 = storeDB.TableNM.Include("Columnss")
.Single(g => g.Tbl_Name == TableIs);
return View(ProjectModel1);
//var ColumnModel = storeDB.TableNM.Find(TableIs);
// return View(ColumnModel);
}
}
Other Classes
public partial class Projects //Partial class, see comment below
{
public int Id { get; set; }
public string Name { get; set; }
public List<Tables> Tabless { get; set; } //Navigation Property, required so that we can include tables under projects
}
public class Tables
{
public int Id { get; set; }
public int ProjectId { get; set; }
public string Tbl_Name { get; set; }
public Projects Project { get; set; } //Class table can have (belong) only one project
public List<Columns> Columnss { get; set; } //Table can have more than one column
}
public class Columns
{
public int Id { get; set; }
[ForeignKey("Tables")]
public int TblId { get; set; }
public string Column_Name { get; set; }
public string IncludeFlag { get; set; }
}
View
<ul>
#foreach (var Tables in Model.Tabless)
{
<li>
#Html.ActionLink(Tables.Tbl_Name, "BrowseColumns", new { TableIs = Tables.Tbl_Name })
</li>
}
Query from SQL profiler
[Project2].[Tables_Id] AS [Tables_Id]
As you can seethe query has a column [Tables_Id] and I do nto understand why it is there as i do nto have any such column. Please help!
Basically MVC3 and EF4 do a lot of things on convention.
My suggestion to make things a little clearer for yourself is read up on EF 4.1 a little, and let it pluralize your table names for you, and use the data annotations (or property mapping if you don't like the attributes in your model) to mark your object's Id properties...
This is not necessarily the cause of your problem, but I think you will find it a lot easier to see what is going on in your profiler and models when the names/values make more logical sense.
Start by singularizing your objects: Table, Column, etc. or even using a more descriptive name... again if for no other reason it will be easier for you to read and debug, or even to get better answers here.
The convention for EF4.1 and foreign keys is to name them {TableName}_{ColumnName} so your foreign key to Tables is expecting a column names Table_Id (because Table is the name of the table, and Id is the name of the PK column.
This might help: EF 4.1 messing things up. Has FK naming strategy changed?