HttpResponseMessage 序列化为 xml

Question

In our application we're having a REST-Api with several controllers like UsersController or UserGroupsController and many more. All calls (get, put, push, delete) on every REST-Endpoint always return a HttpResponseMessage which is always an object of the following type:

public class ComRestResult<T> where T : class
{
   public T Data { get; set; }

   public ValidationItem[] ValidationItems { get; set; }
}

And the ValidationItem -class looks like:

[DataContract]
[Serializable]
public class ValidationItem
{
   [DataMember]
   public string[] ErrorParameters { get; set; }

   [DataMember]
   public ValidationSeverity Severity { get; set; }

   private ValidationId validationId;

   [IgnoreDataMember]
   [XmlIgnore]
   public ValidationId ValidationId
   {
      get { return validationId; }
      set
      {
         validationId = value;
         if(validationId != ValidationId.UnresolvedError)
         {
            legacyValidationId = validationId.ToString();
         }
      }
   }

   private string legacyValidationId;

   [DataMember(Name = "ValidationId")]
   [XmlElement("ValidationId")]
   public string LegacyValidationId
   {
      get { return legacyValidationId; }
      set
      {
         legacyValidationId = value;
         validationId = ValidationId.UnresolvedError;
         ValidationId parsedValidationId;
         if(!string.IsNullOrEmpty(legacyValidationId) && Enum.TryParse(legacyValidationId, out parsedValidationId))
         {
            validationId = parsedValidationId;
         }
      }

ValidationId and Severity are enums.

The Get-Method of the UsersController for example looks like:

[HttpGet]
[Route("")] 
public HttpResponseMessage Get()
{
    RequestHandler handler = new RequestHandler(Request);
    HttpResponseMessage responseMessage = handler.ProcessRequest<User[]>(PersonsAccess.GetAllPersons);
    return responseMessage;
}

The RequestHandler builds the needed HttpResponseMessage and takes a Func<object, T> in it's ProcessRequest-Method.

The HttpResponseMessage is created inside the ProcessRequest-Method with the following line:

HttpResponseMessage httpResponseMessage = request.CreateResponse(httpStatusCode, restResult);

Everything just works fine.

If I look at the response in json it looks like:

{"ValidationItems":[{"ValidationId":"UserIsNew","ErrorParameters":["foo","bar"],"Severity":0,}],"Data":[{"UserId":"ABC123","UserName":"John Smith","IsNew":true},{"UserId":"XYZ789","UserName":"Raimond Test","IsNew":true}]}

This just looks good. Now if I look at the response as xml it looks like:

<ComRestResult xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
  <Data xmlns:d2p1="http://schemas.datacontract.org/2004/07/Comp.Rest.Data.Persons">
    <d2p1:User>
      <d2p1:UserId>ABC123</d2p1:UserId>
      <d2p1:UserName>John Smith</d2p1:UserName>
      <d2p1:IsNew>true</d2p1:IsNew>
    </d2p1:User>
    <d2p1:User>
      <d2p1:UserId>XYZ789</d2p1:UserId>
      <d2p1:UserName>Raimond Test</d2p1:UserName>
      <d2p1:IsNew>true</d2p1:IsNew>
    </d2p1:User>
  </Data>
  <ValidationItems xmlns:d2p1="http://schemas.datacontract.org/2004/07/Comp.BaseInterface.Validation">
    <d2p1:ValidationItem>
      <d2p1:ValidationId>UserIsNew</d2p1:ValidationId>
      <d2p1:ErrorParameters xmlns:d4p1="http://schemas.microsoft.com/2003/10/Serialization/Arrays">
        <d4p1:string>foo</d4p1:string>
        <d4p1:string>bar</d4p1:string>
      </d2p1:ErrorParameters>
      <d2p1:Severity>Information</d2p1:Severity>
    </d2p1:ValidationItem>
  </ValidationItems>
</ComRestResult>

And this looks not good. Although all informations are present we have a problem with the xml-namespaces. The d2p1 and all the others.

If I apply the [DataContract] and [DataMember] attributes at the User -class like:

[DataContract(Name = "User", Namespace = "")]
public class User
{
    [DataMember(Name = "UserId")]
    public string UserId { get; set; }
    [DataMember(Name = "UserName")]
    public string UserName { get; set; }
    [DataMember(Name = "IsNew")]
    public bool IsNew { get; set; }
}

the response-xml for the user looks like:

<Data>
 <User>
  <IsNew>true</IsNew>
  <UserId>ABC123</UserId>
  <UserName>John Smith</UserName>
 </User>
 <User>
  <IsNew>true</IsNew>
  <UserId>XYZ789</UserId>
  <UserName>Raimond Test</UserName>
 </User>
</Data>

That is what we need. But do we really need to apply the attributes on every class, or is there a possibility to deactivate (or so) the namespace at the serialization generally?

Another problem is the string[] in the ValidationItem -class. At the moment this is serialized as:

<d2p1:ErrorParameters xmlns:d4p1="http://schemas.microsoft.com/2003/10/Serialization/Arrays">
    <d4p1:string>foo</d4p1:string>
    <d4p1:string>bar</d4p1:string>
</d2p1:ErrorParameters>

I know I can replace the string[] with the following class:

[CollectionDataContract(ItemName = "value", Namespace = "")]
public class StringArray : List<string>
{
}

But unfortunately this class is very old, is very often used (~4000 references) and is also used for SOAP-Serialization. So we can not easily change it.

There we also need something like a generic serialization to xml without the namespaces.

Answer 1

I solved it by myself.

According to the following article it's possible to use the XmlSerializer instead of the DataContractSerializer . This just works fine.

https://docs.microsoft.com/de-de/aspnet/web-api/overview/formats-and-model-binding/json-and-xml-serialization#xml_media_type_formatter