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public WebClient GetWebClient ()
{
    System.Net.ServicePointManager.Expect100Continue = !DisableExpect100Continue;
    var wc = new WebClient ();
    if ((Address ?? "").Trim ().Length == 0) return wc;
    string a = Address.Trim ();
    if (Port > 0) a += ":" + Port;
    var proxy = new WebProxy { Address = new Uri (a) };            
    if ((Username ?? "").Trim ().Length > 0)
    {
        if ((Domain ?? "").Trim ().Length > 0)
            proxy.Credentials = new NetworkCredential (Username.Trim (), Password, Domain.Trim ());
        else
            proxy.Credentials = new NetworkCredential (Username.Trim (), Password);
    }
    wc.Proxy = proxy;
    return wc;
}