如何通过webapi2将扁平列表返回到breezejs？

Question

I have been struggling with this for a week now. I have a table of Person and Company in the DB. However, there is also a joiner Table of CompanyPerson which has some extra properties like IsPrimaryPerson . Great. Works and all that stuff if I load each thing on it's own into breezejs.

So the problem is that I want to create a list of Persons, but flattened with Companies, like a left outer join, so that I also get each person and company on one line and also include those who do not have a company.

This linq statement in C# gives me that list, I used linqPad to get it working. It's a left outer join sql equivlant.

  from p in Person
    join cp in CompanyPerson
     on p.Id equals cp.PersonId
     into companyPersonGroups
     from cp in companyPersonGroups.DefaultIfEmpty()
    select new {
        Person = p,
        CompanyPerson = cp,
        Company = cp.Company
        }

Great. However what I don't know, is how to get a list like this back to breezejs via the webapi2. Issue one is that the linq returns an anonymnous object. I've tried creating like a ContactPerson object and having properties for Person and Company but I don't know how to get back to breeze since it's not part of the metadata.

Controller, this doesn't work for various reasons depending what I try and do. From "The entity or complex type 'SiteTrackerModel.ContactPerson' cannot be constructed in a LINQ to Entities query" to other problems. Just have it here to show you what I'm trying in a way.

    [BreezeQueryable(MaxExpansionDepth = 3)]
    [HttpGet]
    public IQueryable<ContactPerson> PersonsFlattened()
    {
        //return _contextProvider.QueryAll<Person>();

        var contacts = from person in _contextProvider.QueryAll<Person>()
                       join companyPerson in CompanyPersons() on person.Id equals companyPerson.PersonId into companyPersonGroups
                       from companyPerson in companyPersonGroups.DefaultIfEmpty()
                       select new ContactPerson()
                       {
                           FirstName = person.FirstName,
                           IsPrimaryPerson = companyPerson.IsPrimaryPerson,
                           CompanyName = companyPerson.Company.Name
                       };

        return contacts;

    }

BreezeJs Call in Angular

return EntityQuery.from("PersonsFlattened")
                 //.toType("ContactPerson")
                 .orderBy(orderBy)
                 .using(self.manager).execute()
                 .then(querySucceeded, self._queryFailed);

Here are the classes/tables I'm trying to flatten and return to breeze. I've trimmed down most of the properties

Person.cs (Person Table in Edmx/db)

public partial class Person
{
    public Person()
    {
        this.Companies = new HashSet<CompanyPerson>();
    }

    public int Id { get; set; }
    public string UserName { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }

    public virtual ICollection<CompanyPerson> Companies { get; set; }
}

CompanyPerson.cs (CompanyPerson Table in Edmx/db)

public partial class CompanyPerson
{
    public int PersonId { get; set; }
    public int CompanyId { get; set; }
    public bool IsPrimaryPerson { get; set; }

    public virtual Company Company { get; set; }
    public virtual Person Person { get; set; }
}

Company.cs (Company Table in edmx/db)

public partial class Company
{
    public Company()
    {
        this.Projects = new HashSet<Project>();
        this.PhoneNumbers = new HashSet<CompanyPhoneNumber>();
        this.Addresses = new HashSet<CompanyAddress>();
        this.Persons = new HashSet<CompanyPerson>();
    }

    public int Id { get; set; }
    public string Name { get; set; }

    public virtual ICollection<CompanyPerson> Persons { get; set; }
}

I even tried creating a view in sql that gave me the data, but I can't get Breezejs to figure out what it is but that was just a means to the goal above. A flattened list of people and companies even if they don't have a company.

Answer 1

You can send projection data to BreezeJS and turn them into a custom EntityType you've defined on the client. You can't expect that ContactPerson type to show up in metadata from the server that has been generated by Entity Framework; it's a DTO and not part of the model that EF knows about.

That shouldn't stop you from defining ContactPerson on your Breeze client. Learn about how to create client-side metadata in the docs.

It's worth noting that you do not have to define all of your metadata on the client to take advantage of this feature. Just add this ContactPerson type.

The next trick is getting BreezeJS to realize that your projection data should be transformed into ContactPerson entity on the client.

Breeze won't recognize the anonymous type data by default. You can give it some help with the toType query clause . You can uncomment that clause in your query after you have defined the type in your client metadata .

return EntityQuery.from("PersonsFlattened")
       .toType("ContactPerson") // Should work after defining ContactPerson on client
       .orderBy(orderBy)
       .using(self.manager).execute()
       .then(querySucceeded, self._queryFailed);

You won't need the toType clause if you project into a server-side ContactPerson type and connect the dots between the "PersonsFlattened" endpoint and your custom client-side ContactPerson type in metadata. I think I'd rename that endpoint "ContactPersons" for consistency.

NB : I trust you realize that you've defined read-only types. Breeze doesn't know that so if you make changes to a ContactPerson entity in BreezeJS, the manager will try to save it. Your save attempt will throw on the server unless you catch the incoming change on and do something marvelous with it, perhaps in a BeforeSaveEntity method.

Answer 2

The exception "The entity or complex type 'SiteTrackerModel.ContactPerson' cannot be constructed in a LINQ to Entities query" is related to how the class ContactPerson is declared. LINQ to entity can only construct pur Data Transfert Object : class containing only public properties with trivial getter and setter and without constructor.

Check the ContactPerson class definition.