WCF File Upload Service

Messages

In normal cases you shouldn't have to touch the messages. But in some cases it becomes necessary. For example, assuming that your service will provide a File Upload operation. Here is the possible contract interface:

[OperationContract]
void Upload (string fileName, Stream stream);

Unfortunetly, when using Streams, our operation can not take other parameters. So we cannot tell the fileName to our operation when uploading a file. You may always create two operations, one for setting the fileName, and the other one for uploading the file, but this is not a good solution. In order to solve this problem we will need to create a new message.

[MessageContract]
public class FileMessage
{
  [MessageHeader]
  public string fileName;

  [MessageBody]
  public Stream stream;
}

Our message class needs to have the MessageContract attribute. Since WCF only allows the Stream in message body, we are keeping the fileName in message headers. To keep a data in message header we are using the MessageHeader attribute, and to keep a data in message body we are using the MessageBody attribute.

[OperationContract]
void Upload (FileMessage message);

This is the modified version of our contract.

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