c# - How to serialize an IList<T>?

Question

I've got an OR mapper (iBatis.Net) that returns an IList.

// IList<T> QueryForList<T>(string statementName, object parameterObject);
var data = mapper.QueryForList<Something>(statement, parameters);

I'm trying to use it in an webservice an want to return the data 1:1. Of course I can't return IList in a WebMethod, because it is an interface and therefore not serializable.

I found that the mapper is really returning an List. But I'm afraid to cast it to List because of course the mappers inner workings could change in future versions (and it just feels dirty).

So should I ...

a) return new List<Something>(data);

b) return (List<Something>)data;

c) // your solution here

Thanks a lot!

Answer 1

If it really is a List<T> but you want to protect against change and have it still work, then the most performant solution will be to attempt to cast it to a list, and if that fails then create a new list from its content, e.g.

var data = mapper.QueryForList<T>(statement, parameters);
var list = data as List<T> ?? new List<T>(data);

However, you mention that you can't return an interface because it's a web service. This may have been true with ASMX and the XmlSerializer class, but if you build the web service using WCF and use the DataContractSerializer then it will happily serialize collection interfaces (both as inputs to and outputs from the service). That type of change may be somewhat larger than you're looking for though!