Cannot instantiate the XmlSerializer class

[awa5114]

I'm trying to use the REPL to experiment a little with the objects available in System.Xml.Serialization. I import the namespace, create a simple class and instantiate it:

> using System.Xml.Serialization;

> public class A
  {
      public string MyPublicField = "test";
  }

> A a = new A();

Then I try to create an instance of XmlSerializer along the lines of what is shown in the docs

> XmlSerializer serializer = new XmlSerializer(typeof(A));

Unfortunately this throws an exception:

Identifier 'Submission2' is not CLS-compliant. (Parameter 'ident')

Why does this occur and how can I fix it?