IEnumerable<T> as return type for WCF methods

Question

If i define a Test object, with string and Datetime properties and use it to return IEnumerable(T) collection in WCF

[OperationContract]
IEnumerable<Test> GetTestNotes();

and when calling the service from the client, I see that it is converting the IEnumerable to Test[]:

public Test[] GetTestNotes() {
    return base.Channel.GetTestNotes();
} 

And Im able to get data.

Question is: How reliable is it to use IEnumerable(T) interface rather than concrete, List(T)?

My clients that consume these WCF services are not only in .NET but also in JAVA.

Answer 1

If you're using the Visual Studio generated service references, you can pick what type is used for collections. Right-click on the service under Service References and select Configure Service Reference… . You should see these options:

However, this still won't allow you to select IEnumerable<T> . If you want tighter control over what the client interface looks like, your best bet is to define the contracts in a separate assembly and then reference those assemblies on both the client and server.