Deserialize Abstract Class

Question

I have an abstract class 'Server' which I create in my JavaScript in my UI and then I want to have a method on my Web Service which does the following:

public List<Database> GetDatabases(Server server)
{
    Type type = server.GetType();
    Server x = null;

    if (typeof (SqlServer2005Server).Equals(type))
    {
        x = new SqlServer2005Server();
    }

    // Return the Databases from the server
    return x.GetDatabases();
}

The issue I am having is that Server can not be deserialized as it is abstract, Do I need to have a method for each Server I have which inherits from the concrete type i.e

public List<Database> GetDatabases(SqlServer2005Server server)
{
    // Return the Databases from the server
    return SqlServer2005Serverx.GetDatabases();
}

public List<Database> GetDatabases(OracleServer server)
{
    // Return the Databases from the server
    return SqlServer2005Serverx.GetDatabases();
}

I would really appreciate your help as i am not sure what is the best solution

The exact error I receive is:

Instances of abstract classes cannot be created.

score 9 · Accepted Answer · answered Mar 11 '09 at 11:47

9

WCF will support inheritance, but you need to decorate your data contract with the known type attibute. For example:

[DataContract]
[KnownType(typeof(Customer))]
class Contact
{
   [DataMember]
   public string FirstName
   {get;set;}

   [DataMember]
   public string LastName
   {get;set;}
}
[DataContract]
class Customer : Contact
{
   [DataMember]
   public int OrderNumber
   {get;set;}
}

HTH.

answered Mar 11 '09 at 11:47

stephenl

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Thanks for your reply, can I add several KnowTypes. i.e [DataContract] [KnownType(typeof(Customer))] [KnownType(typeof(Employee))] [KnownType(typeof(Alien))] class Contact { ... Much Appreciated Phill – Phill Duffy Mar 11 '09 at 11:54
Will this also work with Abstract classes, I can see in your example it is a normal class? Thanks again, Phill – Phill Duffy Mar 11 '09 at 11:56
Hi Phil, if you want need to tyou can add as many KnownType attributes as you need. All depends on the depth of your inheritance chain. HTH. Good luck. – stephenl Mar 11 '09 at 22:52
Thanks for the response Steve, I still don't know how to get this to work with the abstract class, which I think is my issue here as I tried the solution you provided to no avail (it will certainly help in the future though). Your help is very much appreciated! – Phill Duffy Mar 12 '09 at 10:16
Hi Phil, no problem. Bear in mind that this is used for inheritance heirarchies. What you may need to do is refactor your code and create a base database class, with SQL and Oracle specializations. You could effectively accomplish the same thing. Good luck! :) – stephenl Mar 13 '09 at 03:56

Deserialize Abstract Class

1 Answers1