Question

Is there a preferable collections object when serializing over WCF? I’m trying to decide between List or IList, and wondering if it makes a difference?

Answer 1

Does not matter from serialization point of view. There is no IList or List on the wire. Both will result in the same XML.

From MSDN:

All list collections of the same type are considered to have the same
data contract (unless they are customized using the
CollectionDataContractAttribute attribute, as discussed later in this
topic).Thus, for example, the following data contracts are equivalent.

[DataContract(Name = "PurchaseOrder")]
public class PurchaseOrder1
{
    [DataMember]
    public string customerName;
    [DataMember]
    public Collection<Item> items;
    [DataMember]
    public string[] comments;
}

[DataContract(Name = "PurchaseOrder")]
public class PurchaseOrder2
{
    [DataMember]
    public string customerName;
    [DataMember]
    public List<Item> items;
    [DataMember]
    public BindingList<string> comments;
}