Sometimes during development I want to have a light-weight approach to logging request and response messages without setting up WCF tracing.​ Regardless of how I am logging (Trace, EntLib, whatever), I need to get a printable version of the data message.

I always recommend treating DataContract classes strictly as data transfer objects (DTO), that is they exist purely for describing the shape of the message on the wire. That means I don’t add any fancy constructors or business logic of any kind to the DTOs. This maintains a separation of concerns. However, all CLR types do have a ToString method, so I an fine with putting it to better use than telling me the name of the type.

In the sample code, CreateSecretRequest overrides ToString using a static helper method, Helper.ToXmlString. That helper method wraps an XmlSerializer and a StringWriter together to serialize the DTO to a string of XML that I can log. All DataContract classes can use the same ToXmlString method to implement their override of ToString in a simple one-liner.

using System.IO;
using System.Xml.Serialization; 

public static class Helper
{
  public static string ToXmlString( object value, string defaultNamespace )
  {
    var writer = new StringWriter();
    (new XmlSerializer( value.GetType(), defaultNamespace )).Serialize( writer, value );
    return writer.ToString();
  }
} 

// a sample data transfer object

using System.Runtime.Serialization; 

[DataContract( Namespace = XmlNamespaces.Secret.CreateSecretRequest )]
public class CreateSecretRequest
{
  [DataMember]
  public string Name { get; set; } 

  [DataMember]
  public string Description { get; set; } 

  public override string ToString()
  { return Helper.ToXmlString( this, XmlNamespaces.Secret.CreateSecretRequest ); }
}

Be careful! This is not the same XML that the service sent or received on the wire. Use WCF Tracing to see what is really happening with your services. This is nearly a 100% genuine approximation of the message, suitable for some quick-and-dirty logging or debugging diagnostics.