自動構成スクリプトを考慮してOSのプロキシ設定をとってくるコード

proxysample.cs

  public partial class MainWindow : Window
  {
    public MainWindow()
    {
      InitializeComponent();
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
      var target = "https://hoge.fuga.example.com/hogehoge/";
      var proxyInfo = CheckProxy(target);
    }

    private ProxyInfo CheckProxy(string targetAddress)
    {
      var targetUri = new Uri(targetAddress);
      var proxyUri = (WebRequest.GetSystemWebProxy()).GetProxy(new Uri(targetAddress));

      if (proxyUri.Host == targetUri.Host)
      {
        // ターゲットとPROXYのHostが同じならProxy無しと判断。
        return new ProxyInfo(false, null);
      }
      else
      {
        // PROXYアリの場合はそのままセット
        return new ProxyInfo(true, proxyUri);
      }
    }

    public class ProxyInfo
    {
      public bool IsUse { get; set; }
      public Uri Uri { get; set; }

      public ProxyInfo()
      {
      }

      public ProxyInfo(bool isUse, Uri uri)
      {
        IsUse = isUse;
        Uri = uri;
      }
    }

  }