I have a project where I need to send a datafile through a web request. We need to setup Two-way authentication also known as mutual authentication. We are not sure if we need a special cert or not but we know that it needs to be level 3.
I am having trouble finding sample code for this case. I don't know where to add our cert information.  With this code a Underlying connection is closed error is thrown when we try to read the response stream and ServicePointManager.ServerCertificateValidationCallback is never called.  Here is what I have:
ServicePointManager.ServerCertificateValidationCallback = New Security.RemoteCertificateValidationCallback(AddressOf MyCertValidationCb)
            httpReq = CType(System.Net.HttpWebRequest.Create(url), HttpWebRequest)
            For Each cert As String In certs
                X509cert = X509Certificate2.CreateFromCertFile(cert)
                X509cert2 = New X509Certificate2(X509cert)
                httpReq.ClientCertificates.Add(X509cert2)
            Next
            httpReq.Method = "POST"        ' Post method
            httpReq.ContentType = "text/xml"               ' content type
            ' Wrap the request stream with a text-based writer
            writer = New StreamWriter(httpReq.GetRequestStream())
            ' Write the XML text into the stream
            reader = New StreamReader(filename.Name)
            ret = reader.ReadToEnd()
            reader.Close()
            ' Send the data to the webserver
            writer.WriteLine(ret)
            writer.Close()
            ' Wait for response
            Dim httpRsp As System.Net.HttpWebResponse = CType(httpReq.GetResponse(), HttpWebResponse)
            sr = New StreamReader(httpRsp.GetResponseStream)
            responseText = sr.ReadToEnd
            If httpReq IsNot Nothing Then
                httpReq.GetRequestStream().Close()
            End If
            If httpRsp IsNot Nothing Then
                httpRsp.GetResponseStream().Close()
            End If
Any tips or links to blogs with sample code would be great. Thanks.