Change location of a type in knowntypes with Backward compatibility

Question

I want to change the assembly of a type but still be backward compatible with old clients for which the type is located in a different assembly

My old known types is

<add type="Messages.GetImageRoutingRulesResponseMessage, Feeder.Data">
      <knownType type="Rules.DicomPushRule, Feeder.Logic" />
</add>

and I changed the location of the DicomPushRule to Feeder.Data , so my new knowntypes will look like this :

<add type="Messages.GetImageRoutingRulesResponseMessage, Feeder.Data">
          <knownType type="Rules.DicomPushRule, Feeder.Data" />
</add>

Will this be backward compatible?

Answer 1

It depend on you contracts.

Let's consider two options:

1. You have two the same class, but in different namespaces:

   DataContract:

   namespace Feeder.Contract
   {
       [DataContract]
       public class DividendBase
       {
           [DataMember]
           public DateTime AnnouncementDate { get; set; }
       }
   }
   
   namespace Feeder.Logic
   {
       [DataContract]
       public class Dividend : DividendBase
       {
           [DataMember]
           public float Amount { get; set; }
           [DataMember]
           public DateTime ExDate { get; set; }
       }
   }
   
   namespace Feeder.Data
   {
       [DataContract]
       public class Dividend : DividendBase
       {
           [DataMember]
           public float Amount { get; set; }
           [DataMember]
           public DateTime ExDate { get; set; }
       }
   }
   

   For this case classes are not compatible, as they have different namespaces and will look differently in xml.

   Serialized in xml:

   <DividendBase i:type="a:Dividend"
                 xmlns="http://schemas.datacontract.org/2004/07/Feeder.Contract"
                 xmlns:i="http://www.w3.org/2001/XMLSchema-instance"
                 xmlns:a="http://schemas.datacontract.org/2004/07/Feeder.Logic">
     <AnnouncementDate>0001-01-01T00:00:00</AnnouncementDate>
     <a:Amount>1.2</a:Amount>
     <a:ExDate>2014-05-20T12:21:42.3608838+03:00</a:ExDate>
   </DividendBase>
   
   <DividendBase i:type="a:Dividend" 
                 xmlns="http://schemas.datacontract.org/2004/07/Feeder.Contract" 
                 xmlns:i="http://www.w3.org/2001/XMLSchema-instance"
                 xmlns:a="http://schemas.datacontract.org/2004/07/Feeder.Data">
     <AnnouncementDate>0001-01-01T00:00:00</AnnouncementDate>
     <a:Amount>1.2</a:Amount>
     <a:ExDate>2014-05-20T12:23:21.2888838+03:00</a:ExDate>
   </DividendBase>
   

2. But if you apply NameSpace attribute for both classes, they will be compatible.

   Data contract with NameSpace in attribute:

   namespace Feeder.Contract
   {
       [DataContract]
       public class DividendBase
       {
           [DataMember]
           public DateTime AnnouncementDate { get; set; }
       }
   }
   
   namespace Feeder.Logic
   {
       [DataContract(Namespace = "Feeder.Contracts")]
       public class Dividend : DividendBase
       {
           [DataMember]
           public float Amount { get; set; }
           [DataMember]
           public DateTime ExDate { get; set; }
       }
   }
   
   namespace Feeder.Data
   {
       [DataContract(Namespace = "Feeder.Contracts")]
       public class Dividend : DividendBase
       {
           [DataMember]
           public float Amount { get; set; }
           [DataMember]
           public DateTime ExDate { get; set; }
       }
   }
   

   And XML for both:

   <DividendBase i:type="a:Dividend" 
                 xmlns="http://schemas.datacontract.org/2004/07/Feeder.Contract"
                 xmlns:i="http://www.w3.org/2001/XMLSchema-instance"
                 xmlns:a="Feeder.Contracts">
     <AnnouncementDate>0001-01-01T00:00:00</AnnouncementDate>
     <a:Amount>1.2</a:Amount>
     <a:ExDate>2014-05-20T12:25:54.7178838+03:00</a:ExDate>
   </DividendBase>
   
   <DividendBase i:type="a:Dividend"
                 xmlns="http://schemas.datacontract.org/2004/07/Feeder.Contract"
                 xmlns:i="http://www.w3.org/2001/XMLSchema-instance"
                 xmlns:a="Feeder.Contracts">
     <AnnouncementDate>0001-01-01T00:00:00</AnnouncementDate>
     <a:Amount>1.2</a:Amount>
     <a:ExDate>2014-05-20T12:26:41.1278838+03:00</a:ExDate>
   </DividendBase>
   

   As you can see, xml's are the same, thus the classes are compatible.

If you have first variant, then, I am afraid, you have incompatible classes.