Question

I’m trying to serialize a NameValueCollection over WCF. I keep getting exceptions telling me to add one type after another. After adding them, I finally get

Type ‘System.Object[]’ cannot be added to list of known types since another type ‘System.Collections.ArrayList’ with the same data contract name ‘http://schemas.microsoft.com/2003/10/Serialization/Arrays:ArrayOfanyType‘ is already present.

The contract now looks like this:

[KnownType(typeof(NameValueCollection))]
[KnownType(typeof(CaseInsensitiveHashCodeProvider))]
[KnownType(typeof(CaseInsensitiveComparer))]
[KnownType(typeof(string[]))]
[KnownType(typeof(Object[]))]
[KnownType(typeof(ArrayList))]
[DataContract]
public class MyClassDataBase
{
    [DataMember]
    public NameValueCollection DataCollection = new NameValueCollection();
}

I really dont know what to do to be able to serialize my NameValueColletion.

Another strange thing is that the compiler warns that the CaseInsensitiveHashCodeProvider is deprecated.

Answer 1

The best idea would be to stop using weak types like NameValueCollection and ArrayList. Use Dictionary<string,string> and List<T> instead.