Try
ret = proxy.IncrementSessionCounter()
Catch we As WebException
'''' We need an HttpWebResponse if we expect to
'''' check the HTTP status code.
If TypeOf we.Response Is HttpWebResponse Then
Dim HttpResponse As HttpWebResponse
HttpResponse = we.Response
If HttpResponse.StatusCode = HttpStatusCode.Found Then
'''' This is a "302 Found" response. Prompt the user
'''' to see if it is okay to redirect.
If MsgBox(String.Format(redirectPrompt, _
HttpResponse.Headers("Location")), _
MsgBoxStyle.YesNo) = _
MsgBoxResult.Yes Then
'''' It is okay. Set the new location and
'''' try again.
webServiceUrl = New Uri(webServiceUrl, _
HttpResponse.Headers("Location"))
Button1_Click(sender, e)
Return
End If
End If
End If
Throw we
End Try
Label1.Text = "Result: " & CStr(ret)
End Sub
And now the ASP.NET session code works as expected. For the purposes
of your own application, you can determine whether you need to prompt a
user for redirecting their HTTP POST request or not. For instance, if
you were calling this code from a service, you would not want to create
a dialog that could not be seen.
This may seem to be a lot of work for getting ASP.NET sessions to
work properly, but be aware that the code shown is useful for other
things as well. For instance, any Web service on any platform that uses
HTTP cookies would require the cookie container code. Similarly, there
may be a host of other reasons why you might receive a "302 Found"
response in reply to your request to a Web service. In a robust
application, there will probably be a number of special scenarios that
you will want to handle when invoking a Web service. Handling cookies
and redirects are two such scenarios you may want to include in your
Web service invocation code on a regular basis.
Conclusion
ASP.NET sessions can be very useful for maintaining state between
Web method calls in your Web service. You do need to be aware that
there may be issues that must be handled by client applications that
you may not see when testing your Web service with the convenient
browser interface. Fortunately, these issues are not particularly hard
to handle.
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