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Collection in WCF

Posted by dj Articles | WCF with C# August 02, 2010
In this article, I will explain How to work with collection in WCF, How to work with concrete collection List, How to work with interface IEnumerable and How to convert Array at client side to collection.
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Objective

In this article, I will explain

  1. How to work with collection in WCF?
  2. How to work with concrete collection List<T> ?
  3. How to work with interface IEnumerable<T> ?
  4. How to convert Array at client side to collection

Collection at service side and client side

WCF1.gif

Since, COLLECTION is very much specific to .Net, so WCF does not expose it to the metadata of the service. But they are very useful, so WCF provides dedicated marshaling rules for collection.

Collection will be exposed as array in service metadata



Let us say, you are having a contract and service implementation as below, If you see carefully, I am returning a collection of the type student

IService1.csWCF2.gif

WCF3.gif

Service1.svc.cs

WCF4.gif

Now when you add this service reference at the client side, you can see the collection is exposed as array. To see this, add the service reference in a client.

I have created a console client and added the service reference of above service. When you click on ServiceReference1 in solution explorer, you can open the proxy code generated at the client side. So click on object browser and you can see that array has been returned in metadata instead of collection.

At the client side



Working with List<T<> or Concrete collection

Imagine a scenario, where return type is concrete collection not an interface. For example, we need to return List<T> instead if IEnumerable<T>
As we know from .Net 3.5 all the classes are by default serialized. And collection we are returning is marked with Serializable not with DataContract.

WCF6.gif

Signature of Add method should be,

WCF7.gif

Let us say,

Contract is,

IService1.cs

WCF8.gif

If you see above, we are returning List<Student> instead of IEnumerable<Student>. So again at the client side, List<Student> would be exposed as Student [] in service metadata.

WCF9.gif

Service implementation is as below,

Service1.svc.cs

WCF10.gif

And again after adding the service reference at the client side, you can see in the object browser List<Student> is exposed as Student[]
So, to call the service at the client side, we need to get the student in array of student

WCF11.gif

So if you see above code, I am taking the output of GetStudents() method in array of student(Student []).

If you want to avoid that, you do not want to use array but instead you want to get collection at the client side.

WCF12.gif

Follow the below steps,

Step 1

While adding the service reference click on Advanced option

WCF13.gif

Step 2

From the drop down of collection type tab, select System.Collections.Generic.List option.

WCF14.gif

Now at the client side,

WCF15.gif

Now you can see at the client side proxy is having list as return not array .

Conclusion

I hope this article was useful to you. Thanks for reading. Happy Coding .
 

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