I am working on a WCF service to provide data to multiple mobile clients. Data model is Entity Framework 4.0. Schema is given below.
When i returnt he object of SysUser the result also contains the navigation properties and EntityKey and other EF related stuff. Is it possible that i get the pure object(only the database fields without the relationship etc).
Thanks
Update
the exception occures "Only parameterless constructors and initializers are supported in LINQ to Entities." on followign code:
return (from u in DataSource.SysUsers
where u.UserID == UserID
select new Player(u)
).FirstOrDefault();
You probably want to send DTOs across the wire rather than your EF objects.
You could use something like AutoMapper to populate your DTOs from the EF objects.
I think if you remove the virtual keyword in your SysUser model for the navigation properties, those will not be loaded. Later, if you need to load this properties, you can do it manually as stated here: http://msdn.microsoft.com/en-us/data/jj574232
Now, if you want to make SysUser travel through a WCF service, it is not a good idea. First, your service's client will need a reference to your Models Project... and that doesn't feels right. If you don't reference your Models, you will get a proxy for it, that is more or less the same as Joe R explained about DTOs.
Here is a related answer: https://stackoverflow.com/a/7161377/7720
Related
I have an ASP.NET MVC 4 project, where Controller calls a WCF Service layer, that calls Business Layer, that use a Repository of EF 5.0 Entities. Then the results are returned as POCO entities to the Controller.
It works fine while the WCF Service is directly referenced as a Library, but I know it won't work referenced as a Service because they will need to be serialized, and with ProxyCreation enabled this is not possible.
I don't want to create DTOs because I use generated POCO entities, that's why they exist in my humble opinion.
I want to track changes only before the POCO entities reach Service layer.
A lot of people talk about using DTOs even when they are identical to POCOs, if I do that, I could create auto-generated copied classes just with different names to be a "Proxy disabled POCO as DTO", what would be a little strange.
Could I kill the proxy class of a POCO, in a way the object could be serialized when returned from the Service layer?
Also I don't know if this idea is a good practice. But would be great to send "clean" entities to my Controllers, ready to me mapped to ViewModels.
I'm looking for performance too.
The problem is solved using ProxyDataContractResolver. We must use [Serializable] and [DataContract(IsReference=true)] too. With this combination, ProxyCreation can be enabled.
The way we handled this was by doing the following:
Customize the T4 generating the POCO classes so that it generates classes decorated with
[Serializable()] and [DataContract(IsReference=true)] attribute.
Both frontend (views) and backend (wcf service / business layer) references the POCO generated classes, since you won't be using proxy due to IsReference=true.
and that's basically it.
With this, you don't have to create DTO and just use the POCO classes both in backend and frontend.
Keep in mind though, that WCF using IsReference=true handles does not like redundant objects (so this would be an issue on some POCO classes with navigation properties).
I have asp.net mvc 2 application. i have confusion creating DTO and domain entities.
MVC Controller Integration points:
1) third party WCF
2) DB Layer
WCF is returning Persons information of a particular company and some information about company.
I have generated proxy of WCF and written a service wrapper on the proxy.
Service wrapper is talking to WCF and Mapping the results to DTO clas ContactsDTO
Service layer is in different project.
Following are my domain classes
Company
Person
DTO class
//it contains
class ContactsDTO
{
Person person, Company[] company
}
Controller action calls the wrapper with companyID and get the object of DTO class.
and update the company information from dto. it updates the company information in Session and pass the Company[]array to some other operations.
DB interaction:
Now depending upon some business logic, i have to insert Person-ids and company id along with some other information in Database.
for this i have created another
class DBDTO
{
Person person, Company[] company, OtherInfo otherInfo[]
}
this DBDTO is prepared and passed to DB Layer(which is using Linq to sql).
Questions
Is it write way to do. Any improvement in DTO interaction? What all
changes i can do to improve the overall architecture
Another alternative to DB-bound objects being translated to DTOs (which takes time) is to use POCO (Plain Old CLR Objects) and use them directly as your Domain Model, objects that can be stored in the DB and objects that are communicated to Controllers for visualization.
This can get you started: Working with POCO Entities
This approach has several advantages
Your POCO entities are independent of the underlying DB implementation
Your POCO entities can be unit-tested without presence of a Database
You can easily serialize them into a service response (if you are building an API) using DataContractSerializer or DataContractJsonSerializer
I agree with Algirdas to differentiate models because of different responsibilities.
By the way: MVC is not a layer concept. It's a concept of three responsibilities and their collaboration. Although it is often (mis)used for layering you will encounter problems with SRP if you only separate your application layers applying "MVC". If you have MVC per layer then you go well.
After all if it is a small application you maybe never reach the critical mass to have problems with the architecture.
I have a DB first EF setup. I would like to return the results of queries and views with WCF services. I have the OperationContracts and the EF classes all have the DataContractAttribute. I can call the method and everything works fine until it goes to return a list of results, then the page goes to "Connection to localhost was interrupted."
I currently work-around this by having a set of DataContract classes that map to the EF classes and they return just fine.
Can anyone tell me how to fix this or why it's happening?
If you're just using the normal code generation strategy for Entity Framework in database-first mode, then those entities cannot be serialized and deserialized, as they rely on the context (which will be destroyed after the call is complete and never exists on the client) to do change tracking.
You need to switch to Self-Tracking Entities.
I'm working on a project where I have an abstract class of Appointment. There are Workouts, Meals and Measurements that all derived from Appointment. My architecture looks like this so far:
Dao - with data access layer being entity framework 4 right now
POCO classes using the T4 templates
WCF
Silverlight Client, ASP.net MVP, mobile clients
Would I put business rules in the POCO class? or map my Entities to a business object with rules and then map those to DTOs and pass those through WCF?? and when I pass the DTOs do I pass over type Appointment? Or write a service method for each sub class like Workout or Meal?
I haven't found any good material using table per type inheritance and WCF.
thanks in advance!
-ajax
it mainly depends on complexity you require. You are using POCO classes it is good starting point. You now have to choose how complex application are you going to build, how much business logic do you want to add and what do you want to expose to your clients?
The POCO entity can be just DTO or you can turn POCO entity into business object by adding business methods and rules directly into that entity - you will transform the entity into Active record pattern or to Domain object. I don't see any reason to map your POCOs to another set of business objects.
Exposing POCO entity in WCF service is the simplest way. You can use operations which will works directly with Appointment class. Additionally you have to give your service information about all classes derived from Appointment - check KnownTypeAttribute and ServiceKnownTypeAttribute. Using entity often means that service calls transport more than is needed - this can be problem for mobile clients with slow internet connection. There is one special point you have to be aware of when exposing entity which is aggregation root (contains references to another entitities and collection of entities) - if you don't have full control over client applications and you allow clients sending full modified object graph you have to validate not only each entity but also that client changed only what he was allowed to. Example: Suppose that client want to modify Order entity. You send him Order with all OrderItem entities and each item will have reference to its Product entity = full object graph. What happens if instead of modifing Order and OrderItems client changes any of Products (for example price)? If you don't check this in your business logic exposed by WCF and pass the modified object graph into EF context, it will modify the price in your database.
If you decide to use your entities like business objects you usually don't expose those entities, instead you will create large set of DTOs. Each operation will work with precisely defined DTO for request and response. That DTO will carry only information which are really needed - this will reduce data payload for service calls and avoid passing modified prices of product, because you will simply define your DTO to not transfer price or even whole product from the client. This solution is much more time consuming to implement and it adds additional layer of complexity.
Because I have mentioned object graphs I must clarify that there is another hidden level of complexity when using them: change tracking. EF context needs to know what have changed in object graph (at least which OrderItem was modified, which was added or deleted, etc.) for correct persistence. Tracking and multi tier solution is a chalenge. The simplest solution does not track changes and instead uses additional query to EF. This query returns actual persisted state of object graph and modified object graph is merged with it (special care is needed for concurrency checks). Other solutions uses some tracking support in entity - check Tracking changes in POCO and Self-tracking entities. But this is only for entities. If you want to track changes in DTO you have to implement your own change tracking. You can also read articles from MSDN magazine about multi tier applications and EF:
Anti-Patterns To Avoid In N-Tier Applications;
Building N-Tier Apps with EF4
I have a server that handles the database access and a client that consumes the information. The communication from the client to the server is through a WCF service.
When the NHibernate POCO is returned from the service are all the objects in the object graph serialized? If so, is there a way to change it?
I'm also thinking of not returning the NHibernate POCO and instead return an object with only the essential information.
What do you do in these cases?
Use data-transfer objects to move the data from the server to the client. Your business (domain model) objects should not necessarily be exposed outside the core of the application, but should be considered a protected asset.
You can use AutoMapper to automate the translation from business objects to data-transfer objects.
Yeah, you probably want a DTO for this. It's usually considered better to not pass your data objects to the outside world, but also passing hibernate objects directly out of a service can give you some weird behavior, especially if you have lazily loaded collections.