Building application with Entity framework dbContext API issues

Question

I am developing a WCF Service application. It is going to be a part of large system. It provides some business logic and is based on Entity framework 4.1. I want to divide application code into 2 tiers (projects in VS, dll's): Service (which contains business logic) and DAL.

I have such database model in my project

ClassModel
classID : int, PK
classIdentity : string
teacherName : string
statisticInfo : int
isRegistered : bool


StudentModel
studentID : int, PK
studentIdentity : string
classID : int, FK

For this I am generating code using dbContext templates and I get:

public partial class ClassModel
{
    public ClassModel()
    {
        this.Student = new HashSet<StudentModel>();
    }
    public int ClassID { get; set; }
    public string ClassIdentity { get; set; }
    public string TeacherName  { get; set; }
    public int StatisticInfo { get; set; }
    public bool IsRegistered { get; set; }

    public virtual ICollection<TerminalModel> Terminal { get; set; }
}

public partial class StudentModel
{
    public int StudentID { get; set; }
    public string StudentIdentity { get; set; }
    public bool IsRegistered { get; set; }

    public virtual ClassModel Class { get; set; }
}

I want to expose only some of this information through the service, so I have different model as a data contract:

[DataContract]
public class Clas{
    [DataMember]
    public string ClassIdentity {get;set;}
    [DataMember]
    public string TeacherName {get;set;}
    [DataMember]
    public string ClassMark {get;set;} //computed from statisticInfo
    [DataMember]
    public int NumberOfStudents {get;set;} //amount of students in this class
}

And my part of my ServiceContract:

[OperationContract]
public void RegsterClass(Clas clas); //(if given clas does not exists adds it and) sets its isRegistered column to True
[OperationContract]
public Clas GetClass(string classIdentity);

As you can see some fields are not present, others are being computed. In such case I have some concerns about how should I built application properly. Could you write example code which implements the interface methods using everything I mentioned in the way that you think is proper?

"Could you write example code which implements the interface methods using everything I mentioned in the way that you think is proper?" I think you should be more specific with your questions. If you are posting conceptual questions - consider asking them in a technology-neutral way. It seems like your question has little to do with WCF or EF specifically. Try to break the question down into a few smaller and more specific ones. (I find this helps to get answers) — Andriy Drozdyuk

reckface reckface · Accepted Answer · 2012-10-11T08:49:44

Try using T4 templates

It is possible to use T4 templates to generate the dbContext classes, the data transfer objecs (more on that later), the interface as well as all the two methods you have there for each entity in your model: RegsterClass and GetClass. (this would translate to RegsterStudent, GetStudent, and so on for every entity) Then you can use AutoMapper on NuGet to map from Clas to ClassModel.

I've implemented something similar. I don't pass any of my dbcontext based entities across the wire. I use Data transfer objects for each entity. So a Toyota entity, has a ToyotaDto that has the data annotations and is used for all the WCF CRUD operations. When "Getting" a toyotaDto, I map Toyota to ToyotaDto and return the Dto, when saving, I map the Dto to an entity, of course deleting is done by key, so no Dto necessary. There are several(1) good(2) examples(3) online you can modify to suit, and if you want I can paste in some of the templates I'm using.

Building application with Entity framework dbContext API issues

1 Answers