Question

In order to log some HTTP traffic I’m trying to serialize an instance of System.Net.HttpWebRequest. The application uses MVC 3 and the problem code is in an action method in a controller class.

In .NET Framework 4 it the class is documented as serializable:

[SerializableAttribute]
  public class HttpWebRequest : WebRequest, 
      ISerializable

The following test code fails at the indicated statement:

...
HttpWebRequest preapprovalRequest = (HttpWebRequest)WebRequest.Create("http://big.URL.here");
...
HttpWebResponse preapprovalResponse = (HttpWebResponse)preapprovalRequest.GetResponse();


// Serialize the request context.
IFormatter formatter = new BinaryFormatter();
MemoryStream msRequest = new MemoryStream();
formatter.Serialize(msRequest, preapprovalRequest); //<<<<< Error here.
// Reset the stream and deserialize.
msRequest.Seek(0, SeekOrigin.Begin);
HttpWebRequest duplicateRequest = (HttpWebRequest)formatter.Deserialize(msRequest);
msRequest.Close();

// Serialize the response context.
MemoryStream msResponse = new MemoryStream();
formatter.Serialize(msResponse, preapprovalResponse);
// Reset the stream and deserialize.
msResponse.Seek(0, SeekOrigin.Begin);
HttpWebResponse duplicateResponse = (HttpWebResponse)formatter.Deserialize(msResponse);
msResponse.Close();

The error reported is:

Type 'System.Net.WebRequest+WebProxyWrapper' in Assembly
'System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'
is not marked as serializable.

I’ve tried chasing WebProxyWrapper with no joy. Just a bit of unhelpful baggage. Explicitly casting the HttpWebRequest to a WebRequest doesn’t alter the error:

formatter.Serialize(msRequest, (WebRequest)preapprovalRequest);

On the bright side, the code does properly serialize and deserialize the instance of HttpWebResponse.

How can I lose the wrapper? Is there a better approach?

Answer 1

The official answer from Microsoft:

Thank you for your feedback. Unfortunately HttpWebRequest dropped
support for serialization after .NET 1.1. See
http://msdn.microsoft.com/en-us/library/system.net.httpwebrequest.httpwebrequest(v=VS.100).aspx

We’ll see if we can get that attribute removed to avoid this confusion
in the future.

They changed the documentation to include the [ObsoleteAttribute] attribute.