Question

I have the following code

namespace A
{
    [DataContract]
    public class CustomClass {}
}

how could I decorate the DataContract attribute, or what I must change on server side to change the code into

namespace B
{
    [DataContract(...)]
    public class CustomClass {}
}

and all existing clients to connect without problems to this client.

Note: I can’t change any client, only on server side.

Answer 1

That depends on what binding (and more specifically, which serializer) you are using. If you are using DataContractSerializer, then the answer is simple: do nothing. Those two contracts are equivalent; the wire data is defined by:

• the explicit name in [DataContract(...)], if one – else the class name (which matches)
• the explicit xml namespace in [DataContract(...)]

If you are using NetDataContractSerializer, simple: you can’t.

Note that the c# namespace used at the client is entirely up to the client, and is typically determined by the tooling used to generate the type. Frankly, it doesn’t matter what the client uses as the c# namespace, as long as they are using a contract-based serializer such as XmlSerializer or DataContractSerializer.

To illustrate this: this prints the same thing twice:

using System.Runtime.Serialization;
using System;
namespace A
{
    [DataContract] class Foo { }
}
namespace B
{
    [DataContract] class Foo { }
}
static class Program
{
    static void Main()
    {
        new DataContractSerializer(typeof (A.Foo)).WriteObject(
              Console.OpenStandardOutput(), new A.Foo());
        Console.WriteLine();
        new DataContractSerializer(typeof (B.Foo)).WriteObject(
              Console.OpenStandardOutput(), new B.Foo());
    }
}