WCF序列化/反序列化List <>

Question

Here's the code I did first (which is not working), my question will follow the code.

[DataContract]
public class ValidationData
{
   [DataMember]
   public bool IsValid { get; set; }

   [DataMember]
   public List<string> Messages { get; set; }
}


[DataContract]
public class Parameters
{
   [DataMember]
   public string Name { get; set; }

   [DataMember]
   public ValidationData ValidationData { get; set; }
}


[ServiceContract]
public interface IValidation
{
   [OperationContract]
   void Validate(Parameters parameters);
}

public class Validation : IValidation
{
   public void Validate(Parameters parameters)
   {
      bool valid = someClass.DoValidation(parameters.Name);

      parameters.ValidationData.IsValid = valid;

      if(!valid)
         parameters.ValidationData.Messages.Add("some validation message");
   }
}

On the client side I called the service that way :

var service = new WcfService.ValidationService();
var parameters = new WcfService.Parameters();

parameters.Name = "some name to validate";
parameters.ValidationData = new WcfService.ValidationData();
parameters.ValidationData.Messages = new List<string>();

service.SynchronizeDatabase(parameters);

if(!parameters.ValidationData.IsValid)
   ShowMessage(string.join(Environnement.NewLine, parameters.ValidationData.Messages));

Using that code, when I look at parameters.ValidationData on the client side, I have the good value for the field IsValid , but the list is always empty no matter the value of IsValid .

I know it wasn't the best way of doing it, that's why I changed it. Now it's working and the service contract looks like :

[ServiceContract]
public interface IValidation
{
   [OperationContract]
   ValidationData Validate(Parameters parameters); // changed void to ValidationData
}

and the parameters data contracts is now :

[DataContract]
public class Parameters // Removed the ValidationData member
{
   [DataMember]
   public string Name { get; set; }
}

And finally the implementation of the operation contract :

public class Validation : IValidation
{
   public ValidationData Validate(Parameters parameters)
   {
      var validations = new ValidationData(); // in the constructor I initialize the list

      validations.IsValid = someClass.DoValidation(parameters.Name);

      if(!validations.IsValid)
         validations.Messages.Add("some validation message");

      return validations;
   }

}

My question is why the list is always empty if it's included in the parameters list sent by the client (first way I did this). And it's not when the ValidationData object is created server side and returned by the operation contract? I'm just looking for an explanation here, as I already solved my problem.

(Feel free to close it if it don't belongs here...)

Answer 1

If I understand correctly, you are modifying the list on the server, and you expect that you can read those changes on the client side. You need to specify the parameter as ref . This way, changes made on the server will come back to the client. Otherwise they won't, you will only see on the client side what you originally put in the list, so it will be empty in your case. Ie.

void Validate(ref Parameters parameters);