Inherit HttpWebRequest?

[Fred W]

I'm attempting to inherit HttpWebRequest. For argument's sake let's say
that one string property will be added.
The constructor does not take explicit overloads so I'm looking at the
static Create method.
Is it possible?

public class CustomHttpWebRequest : HttpWebRequest
{
//additional property
public string NewValue;

public CustomHttpWebRequest (SerializationInfo si, StreamingContext sc)
: base (si, sc)
{//required for successful compile
}

public static new CustomHttpWebRequest Create(string uri, string
newValue)
{
//how is this done?
CustomHttpWebRequest custReq =
(CustomHttpWebRequest)HttpWebRequest.Create(uri);

custReq.NewValue = newValue;
return custReq;
}

//this won't compile
//public CustomHttpWebRequest(string newValue)
//{
// NewValue = newValue;
//}
}