WCF Message Contract and Streaming

Question

I'm going boarder line crazy, I have been working with this for over a day and still have no idea why it doesn't work,

I have a MessageContract that I'm using to send out a stream, but I get the following error,

Type 'System.IO.FileStream' with data contract name 'FileStream:http://schemas.datacontract.org/2004/07/System.IO' is not expected. Add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to DataContractSerializer.

[ServiceContract()]
public interface IContentService
{
    [OperationContract(), FaultContract(typeof(ContentFault))]
    PublishItemResponse PublishFile(PublishFileRequest request);
}


[MessageContract()]
public class PublishFileRequest
{ 
 [MessageHeader()]
 public FileInventoryItem Item {get;set;}

 [MessageHeader()]
 public Request Request  {get;set;}

 [MessageBodyMember()]
 public Stream FileContent {get;set;}
}



 [MessageContract()]
 public class Request
 {
  [MessageHeader()]
  public Guid AuthorizationToken { get; set; }

  [MessageHeader()]
  public string CoreVersion  { get; set; }

  [MessageHeader()]
  public string Password { get; set; }

  [MessageHeader()]
  public DateTime RequestTime { get; set; }

  [MessageHeader()]
  public string ComponentVersion { get; set; }

  [MessageHeader()]
  public string UserName  { get; set; }
 }



[MessageContract()]
[Serializable()]
public class FileInventoryItem : InventoryItemBase
{
 public Stream FileContent { get; set;}
}



[MessageContract()]
[KnownType(typeof(FileInventoryItem))]
[KnownType(typeof(FolderInventoryItem))]
[Serializable()]
public abstract class InventoryItemBase
{
 public List<string> Errors {get;set;}

 public List<string> Warnings  {get;set;}

 [MessageHeader()]
 public StagingAction Action {get;set;}

 [MessageHeader()]
 public string ContentXml  {get;set;}

 [MessageHeader()]
 public int ItemId {get;set;}

 [MessageHeader()]
 public ItemType ItemType { {get;set;}

 [MessageHeader()]
 public string Name  {get;set;}

 [MessageHeader()]
 public int ParentId {get;set;}

 [MessageHeader()]
 public Guid ParentUniqueId  {get;set;}

 [MessageHeader()]
 public Guid UniqueId  {get;set;}

 [MessageHeader()]
 public Guid Version  {get;set;}
}

Any help is greatly appropriated,

Answer 1

FileStream is not serializable, this may be causing the issue.

Do you know the size of the input file contents? If large then this may not be feaseable, but have you tested with a MemoryStream as the Stream object?

Answer 2

WCF requires the types that are serialized to exactly match the types that are declared in the contract. You can get around that by adding the KnownType attribute to indicate that you know a particular sub type is going to be used (in this case you would add it to the PublishFileRequest class).

However, while that will eliminate the first error, your code will still not work, since FileStreams are not serializable.