if ( proxyUsername != null && proxyPassword != null )
{
Credentials creds;
if ( proxyNtlmHost != null || proxyNtlmDomain != null )
{
creds = new NTCredentials( proxyUsername, proxyPassword, proxyNtlmHost, proxyNtlmDomain );
}
else
{
creds = new UsernamePasswordCredentials( proxyUsername, proxyPassword );
}